[CI] Fix install llvm in mingw-w64.yml (crystal-lang#15476)

The second package iteration of `crystal` package removes `llvm` and only depends on `lib-llvm`, so we need to install it explicitly.

msys2/MINGW-packages#23360

Author: straight-shoota

.github/workflows/mingw-w64.yml

@@ -25,6 +25,7 @@ jobs:
             git
             make
             mingw-w64-ucrt-x86_64-pkgconf
+            mingw-w64-ucrt-x86_64-llvm
             mingw-w64-ucrt-x86_64-crystal
 
       - name: Disable CRLF line ending substitution
@@ -81,6 +82,7 @@ jobs:
             git
             make
             mingw-w64-ucrt-x86_64-pkgconf
+            mingw-w64-ucrt-x86_64-llvm
             mingw-w64-ucrt-x86_64-crystal
 
       - name: Disable CRLF line ending substitution
@@ -109,6 +111,7 @@ jobs:
             git
             make
             mingw-w64-ucrt-x86_64-pkgconf
+            mingw-w64-ucrt-x86_64-llvm
             mingw-w64-ucrt-x86_64-crystal
 
       - name: Disable CRLF line ending substitution