[libc] Replace -nostdlib++ flag when building with gcc and add placement new

operator to HermeticTestUtils.cpp.

Author: lntue

libc/cmake/modules/LLVMLibCTestRules.cmake

@@ -564,8 +564,10 @@ function(add_integration_test test_name)
 
   if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
     target_link_options(${fq_build_target_name} PRIVATE -nostdlib -static)
-  else()
+  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
     target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib++ -static)
+  else()
+    target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib -static)
   endif()
   target_link_libraries(
     ${fq_build_target_name}
@@ -741,8 +743,10 @@ function(add_libc_hermetic_test test_name)
 
   if(LIBC_TARGET_ARCHITECTURE_IS_GPU)
     target_link_options(${fq_build_target_name} PRIVATE -nostdlib -static)
-  else()
+  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
     target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib++ -static)
+  else()
+    target_link_options(${fq_build_target_name} PRIVATE -nolibc -nostartfiles -nostdlib -static)
   endif()
   target_link_libraries(
     ${fq_build_target_name}

libc/test/UnitTest/HermeticTestUtils.cpp

@@ -104,6 +104,8 @@ void *__dso_handle = nullptr;
 
 } // extern "C"
 
+void *operator new(unsigned long size, void *ptr) { return ptr; }
+
 void *operator new(size_t size) { return malloc(size); }
 
 void *operator new[](size_t size) { return malloc(size); }
@@ -113,3 +115,5 @@ void operator delete(void *) {
   // we just trap here to catch any such accidental usages.
   __builtin_trap();
 }
+
+void operator delete(void *ptr, size_t size) { __builtin_trap(); }