gnu: Add gcc-toolchain-11.

* gnu/packages/gcc.scm (gcc-11): New variable.
* gnu/packages/commencement.scm (gcc-toolchain-11): New variable.

gnu/packages/commencement.scm

@@ -3936,6 +3936,9 @@ is the GNU Compiler Collection.")
 (define-public gcc-toolchain-10
   (make-gcc-toolchain gcc-10))
 
+(define-public gcc-toolchain-11
+  (make-gcc-toolchain gcc-11))
+
 (define-public gcc-toolchain-aka-gcc
   ;; It's natural for users to try "guix install gcc".  This package
   ;; automatically "redirects" them to 'gcc-toolchain'.

gnu/packages/gcc.scm

@@ -594,6 +594,20 @@ It also includes runtime support libraries for these languages.")))
             (patches (search-patches "gcc-9-strmov-store-file-names.patch"
                                      "gcc-5.0-libvtv-runpath.patch"))))))
 
+(define-public gcc-11
+  (package
+   (inherit gcc-8)
+   (version "11.1.0")
+   (source (origin
+            (method url-fetch)
+            (uri (string-append "mirror://gnu/gcc/gcc-"
+                                version "/gcc-" version ".tar.xz"))
+            (sha256
+             (base32
+              "1pwxrjhsymv90xzh0x42cxfnmhjinf2lnrrf3hj5jq1rm2w6yjjc"))
+            (patches (search-patches "gcc-9-strmov-store-file-names.patch"
+                                     "gcc-5.0-libvtv-runpath.patch"))))))
+
 ;; Note: When changing the default gcc version, update
 ;;       the gcc-toolchain-* definitions.
 (define-public gcc gcc-7)