gnu: LLVM, Clang: Add 11.0.0.

* gnu/packages/patches/clang-11.0-libc-search-path.patch: New file.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.
* gnu/packages/llvm.scm (llvm-11, clang-runtime-11, clang-11,
clang-toolchain-11): New variables.

gnu/local.mk

@@ -861,6 +861,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/clang-7.0-libc-search-path.patch		\
   %D%/packages/patches/clang-9.0-libc-search-path.patch		\
   %D%/packages/patches/clang-10.0-libc-search-path.patch	\
+  %D%/packages/patches/clang-11.0-libc-search-path.patch	\
   %D%/packages/patches/clang-runtime-asan-build-fixes.patch	\
   %D%/packages/patches/clang-runtime-esan-build-fixes.patch	\
   %D%/packages/patches/clang-runtime-9-libsanitizer-mode-field.patch	\

gnu/packages/llvm.scm

@@ -450,17 +450,17 @@ output), and Binutils.")
               ("libc-debug" ,glibc "debug")
               ("libc-static" ,glibc "static")))))
 
-(define-public llvm-10
+(define-public llvm-11
   (package
     (name "llvm")
-    (version "10.0.0")
+    (version "11.0.0")
     (source
      (origin
       (method url-fetch)
       (uri (llvm-uri "llvm" version))
       (sha256
        (base32
-        "1pwgm6cr0xr5a0hrbqs1zvsvvjvy0yq1y47c96804wcs795s90yz"))))
+        "0s94lwil98w7zb7cjrbnxli0z7gklb312pkw74xs1d6zk346hgwi"))))
     (build-system cmake-build-system)
     (outputs '("out" "opt-viewer"))
     (native-inputs
@@ -512,6 +512,39 @@ languages is in development.  The compiler infrastructure includes mirror sets
 of programming tools as well as libraries with equivalent functionality.")
     (license license:asl2.0)))  ;with LLVM exceptions, see LICENSE.txt
 
+(define-public clang-runtime-11
+  (clang-runtime-from-llvm
+   llvm-11
+   "0d5j5l8phwqjjscmk8rmqn0i2i0abl537gdbkagl8fjpzy1gyjip"))
+
+(define-public clang-11
+  (clang-from-llvm llvm-11 clang-runtime-11
+                   "02ajkij85966vd150iy246mv16dsaph1kfi0y8wnncp8w6nar5hg"
+                   #:patches '("clang-11.0-libc-search-path.patch")
+                   #:tools-extra
+                   (origin
+                     (method url-fetch)
+                     (uri (llvm-uri "clang-tools-extra"
+                                    (package-version llvm-11)))
+                     (sha256
+                      (base32
+                       "02bcwwn54661madhq4nxc069s7p7pj5gpqi8ww50w3anbpviilzy")))))
+
+(define-public clang-toolchain-11
+  (make-clang-toolchain clang-11))
+
+(define-public llvm-10
+  (package
+    (inherit llvm-11)
+    (version "10.0.0")
+    (source
+     (origin
+      (method url-fetch)
+      (uri (llvm-uri "llvm" version))
+      (sha256
+       (base32
+        "1pwgm6cr0xr5a0hrbqs1zvsvvjvy0yq1y47c96804wcs795s90yz"))))))
+
 (define-public clang-runtime-10
   (clang-runtime-from-llvm
    llvm-10

gnu/packages/patches/clang-11.0-libc-search-path.patch

@@ -0,0 +1,89 @@
+Clang attempts to guess file names based on the OS and distro (yes!),
+but unfortunately, that doesn't work for us.
+
+This patch makes it easy to insert libc's $libdir so that Clang passes the
+correct absolute file name of crt1.o etc. to 'ld'.  It also disables all
+the distro-specific stuff and removes the hard-coded FHS directory names
+to make sure Clang also works on non-Guix systems.
+
+diff --git a/lib/Driver/ToolChains/Gnu.cpp b/lib/Driver/ToolChains/Gnu.cpp
+--- a/lib/Driver/ToolChains/Gnu.cpp
++++ b/lib/Driver/ToolChains/Gnu.cpp
+@@ -2797,7 +2797,7 @@ void Generic_GCC::AddMultilibPaths(const Driver &D,
+     // the cross. Note that GCC does include some of these directories in some
+     // configurations but this seems somewhere between questionable and simply
+     // a bug.
+-    if (StringRef(LibPath).startswith(SysRoot)) {
++    if (0) {
+       addPathIfExists(D, LibPath + "/" + MultiarchTriple, Paths);
+       addPathIfExists(D, LibPath + "/../" + OSLibDir, Paths);
+     }
+@@ -2811,6 +2811,10 @@ void Generic_GCC::AddMultiarchPaths(const Driver &D,
+   // Try walking via the GCC triple path in case of biarch or multiarch GCC
+   // installations with strange symlinks.
+   if (GCCInstallation.isValid()) {
++
++// The following code would end up adding things like
++// "/usr/lib/x86_64-unknown-linux-gnu/../../lib64" to the search path.
++#if 0
+     addPathIfExists(D,
+                     SysRoot + "/usr/lib/" + GCCInstallation.getTriple().str() +
+                         "/../../" + OSLibDir,
+@@ -2823,6 +2827,7 @@ void Generic_GCC::AddMultiarchPaths(const Driver &D,
+           D, GCCInstallation.getInstallPath() + BiarchSibling.gccSuffix(),
+                       Paths);
+     }
++#endif // Guix
+ 
+     // See comments above on the multilib variant for details of why this is
+     // included even from outside the sysroot.
+diff --git a/lib/Driver/ToolChains/Linux.cpp b/lib/Driver/ToolChains/Linux.cpp
+--- a/lib/Driver/ToolChains/Linux.cpp
++++ b/lib/Driver/ToolChains/Linux.cpp
+@@ -219,6 +219,9 @@ Linux::Linux(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
+ 
+   Generic_GCC::PushPPaths(PPaths);
+ 
++// Comment out the distro-specific tweaks so that they don't bite when
++// using Guix on a foreign distro.
++#if 0
+   Distro Distro(D.getVFS(), Triple);
+ 
+   if (Distro.IsAlpineLinux() || Triple.isAndroid()) {
+@@ -284,6 +287,7 @@ Linux::Linux(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
+ 
+   if (IsAndroid || Distro.IsOpenSUSE())
+     ExtraOpts.push_back("--enable-new-dtags");
++#endif	// Guix
+ 
+   // The selection of paths to try here is designed to match the patterns which
+   // the GCC driver itself uses, as this is part of the GCC-compatible driver.
+@@ -310,6 +314,8 @@ Linux::Linux(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
+   addPathIfExists(D, SysRoot + "/lib/" + MultiarchTriple, Paths);
+   addPathIfExists(D, SysRoot + "/lib/../" + OSLibDir, Paths);
+ 
++// This requires the commented distro tweaks above.
++#if 0
+   if (IsAndroid) {
+     // Android sysroots contain a library directory for each supported OS
+     // version as well as some unversioned libraries in the usual multiarch
+@@ -338,6 +344,7 @@ Linux::Linux(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
+     addPathIfExists(D, SysRoot + "/" + OSLibDir + "/" + ABIName, Paths);
+     addPathIfExists(D, SysRoot + "/usr/" + OSLibDir + "/" + ABIName, Paths);
+   }
++#endif // Guix
+ 
+   Generic_GCC::AddMultiarchPaths(D, SysRoot, OSLibDir, Paths);
+ 
+@@ -349,8 +356,9 @@ Linux::Linux(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
+   if (StringRef(D.Dir).startswith(SysRoot))
+     addPathIfExists(D, D.Dir + "/../lib", Paths);
+ 
+-  addPathIfExists(D, SysRoot + "/lib", Paths);
+-  addPathIfExists(D, SysRoot + "/usr/lib", Paths);
++  // Add libc's lib/ directory to the search path, so that crt1.o, crti.o,
++  // and friends can be found.
++  addPathIfExists(D, "@GLIBC_LIBDIR@", Paths);
+ }
+ 
+ ToolChain::CXXStdlibType Linux::GetDefaultCXXStdlibType() const {