Our llvm include path is not in the include list tried by default.

--- zig-0.7.1.orig/cmake/Findllvm.cmake
+++ zig-0.7.1/cmake/Findllvm.cmake
@@ -12,6 +12,7 @@
     /usr/lib/llvm/11/include
     /usr/lib/llvm-11/include
     /usr/lib/llvm-11.0/include
+    /usr/lib/llvm11/include
     /usr/local/llvm11/include
     /usr/local/llvm110/include
     /mingw64/include