[Clang] use unsigned integer constants in unit-test | fixes build err…

…or on ppc64le-lld-multistage-test

Fixes:
    /home/buildbots/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/third-party/unittest/googletest/include/gtest/gtest.h:1526:11: warning: comparison of integer expressions of different signedness: ‘const unsigned int’ and ‘const int’ [-Wsign-compare]
    /home/buildbots/ppc64le-lld-multistage-test/ppc64le-lld-multistage-test/llvm-project/third-party/unittest/googletest/include/gtest/gtest.h:1526:11: warning: comparison of integer expressions of different signedness: ‘const long unsigned int’ and ‘const int’ [-Wsign-compare]

Reviewed By: cor3ntin

Differential Revision: https://reviews.llvm.org/D156224

clang/unittests/libclang/LibclangTest.cpp

@@ -1220,7 +1220,7 @@ static_assert(true, message);
   const char *Args[] = {"-xc++", "-std=c++26"};
   ClangTU = clang_parseTranslationUnit(Index, fileName.c_str(), Args,
                                        std::size(Args), nullptr, 0, TUFlags);
-  ASSERT_EQ(clang_getNumDiagnostics(ClangTU), 0);
+  ASSERT_EQ(clang_getNumDiagnostics(ClangTU), 0u);
   std::optional<CXCursor> staticAssertCsr;
   Traverse([&](CXCursor cursor, CXCursor parent) -> CXChildVisitResult {
     if (cursor.kind == CXCursor_StaticAssert) {
@@ -1229,7 +1229,7 @@ static_assert(true, message);
     return CXChildVisit_Continue;
   });
   ASSERT_TRUE(staticAssertCsr.has_value());
-  size_t argCnt = 0;
+  int argCnt = 0;
   Traverse(*staticAssertCsr, [&argCnt](CXCursor cursor, CXCursor parent) {
     switch (argCnt) {
     case 0: