llvm: migrate to pkgconf

Author: cho-m

Formula/l/llvm.rb

@@ -49,14 +49,11 @@ class Llvm < Formula
   uses_from_macos "zlib"
 
   on_linux do
-    depends_on "pkg-config" => :build
+    depends_on "pkgconf" => :build
     depends_on "binutils" # needed for gold
     depends_on "elfutils" # openmp requires <gelf.h>
   end
 
-  # Fails at building LLDB
-  fails_with gcc: "5"
-
   # Support simplified triples in version config files.
   # https://github.com/llvm/llvm-project/pull/111387
   patch do
@@ -767,10 +764,10 @@ def caveats
 
     # This will fail if the clang bindings cannot find `libclang`.
     with_env(PYTHONPATH: prefix/Language::Python.site_packages(python3)) do
-      system python3, "-c", <<~EOS
+      system python3, "-c", <<~PYTHON
         from clang import cindex
         cindex.Config().get_cindex_library()
-      EOS
+      PYTHON
     end
 
     unless versioned_formula?