Revert "[gn build] (manually) port 83a798d4b0 (abi_breaking_checks in tests)"

This reverts commit edddf384c2.
83a798d4b0 was reverted in 62a983ebc5.

llvm/utils/gn/build/buildflags.gni

@@ -29,9 +29,6 @@ declare_args() {
   # Whether to build with optimizations.
   is_optimized = !is_debug
 
-  # Enable additional checks that alter the LLVM C++ ABI.
-  llvm_enable_abi_breaking_checks = llvm_enable_assertions
-
   # Debug info symbol level.
   if (is_debug) {
     symbol_level = 2

llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn

@@ -42,6 +42,9 @@ import("//llvm/version.gni")
 # become declare_args if anyone wants to set them.
 
 declare_args() {
+  # Enable additional checks that alter the LLVM C++ ABI.
+  llvm_enable_abi_breaking_checks = llvm_enable_assertions
+
   # Iterate unordered llvm containers in reverse.
   llvm_enable_reverse_iteration = false
 

llvm/utils/gn/secondary/llvm/test/BUILD.gn

@@ -197,12 +197,6 @@ write_lit_config("lit_site_cfg") {
     extra_values += [ "LLVM_ENABLE_EXPENSIVE_CHECKS=0" ]  # Must be 0.
   }
 
-  if (llvm_enable_abi_breaking_checks) {
-    extra_values += [ "LLVM_ENABLE_ABI_BREAKING_CHECKS=1" ]
-  } else {
-    extra_values += [ "LLVM_ENABLE_ABI_BREAKING_CHECKS=0" ]  # Must be 0.
-  }
-
   if (llvm_enable_threads) {
     extra_values += [ "LLVM_ENABLE_THREADS=1" ]
   } else {