[ci] Use git utest for haxe 5 test suite (#1270)

The setup step already installs the git libraries, so this overrides
those. For haxe 5, we need to use git utest for int64 support.

For haxe 4, continue to use the haxelib release as the tests don't
compile with git utest.

Author: tobil4sk

.github/workflows/test.yml

@@ -227,6 +227,8 @@ jobs:
           haxe: ${{ inputs.haxe }}
       - name: install haxe libs
         run: haxelib install compile-cpp.hxml --always
+        # haxe 4 tests don't build with latest utest
+        if: inputs.haxe != 'latest'
       - name: build
         run: haxe compile-cpp.hxml -D ${{ env.HXCPP_ARCH_FLAG }} -D no_http
       - name: run