gnu: Add ocaml-llvm.

* gnu/packages/ocaml.scm (make-ocaml-llvm, ocaml-llvm, ocaml-llvm-9)
(ocaml-llvm-10, ocaml-llvm-11): New variables.

gnu/packages/ocaml.scm

@@ -6197,3 +6197,44 @@ provides support to program with time varying values: declarative events and
  signals.  React doesn't define any primitive event or signal, it lets the
 client chooses the concrete timeline.")
     (license license:lgpl2.1+)))
+
+(define (make-ocaml-llvm llvm)
+  (package
+    (inherit llvm)
+    (name "ocaml-llvm")
+    (outputs '("out"))
+    (arguments
+     `(#:configure-flags
+       (list
+         (string-append "-DLLVM_OCAML_EXTERNAL_LLVM_LIBDIR="
+                        (assoc-ref %build-inputs "llvm") "/lib")
+         "-DBUILD_SHARED_LIBS=TRUE"
+         "-DLLVM_OCAML_OUT_OF_TREE=TRUE"
+         (string-append "-DLLVM_OCAML_INSTALL_PATH="
+                        (assoc-ref %outputs "out") "/lib/ocaml/site-lib"))
+       #:phases
+       (modify-phases %standard-phases
+         (replace 'build
+           (lambda _
+             (invoke "make" "ocaml_all")))
+         (replace 'install
+           (lambda _
+             (invoke "cmake" "-P" "bindings/ocaml/cmake_install.cmake"))))))
+    (inputs
+     `(("llvm" ,llvm)))
+    (native-inputs
+     `(("ocaml" ,ocaml)
+       ("ocaml-findlib" ,ocaml-findlib)
+       ("ocaml-ounit" ,ocaml-ounit)
+       ("python" ,python)))
+    (propagated-inputs
+     `(("ocaml-integers" ,ocaml-integers)
+       ("ocaml-ctypes" ,ocaml-ctypes)))
+    (synopsis "OCaml bindings to LLVM")
+    (description "This package contains the OCaml bindings distributed with
+LLVM.")))
+
+(define-public ocaml-llvm (make-ocaml-llvm llvm))
+(define-public ocaml-llvm-9 (make-ocaml-llvm llvm-9))
+(define-public ocaml-llvm-10 (make-ocaml-llvm llvm-10))
+(define-public ocaml-llvm-11 (make-ocaml-llvm llvm-11))