Reland "[lldb][lit] Add MallocNanoZone envvar to Darwin ASan builds" … (llvm#88442)

…(llvm#88436)"

This reverts commit 1f5d130. The
original commit checks that the host system is "Darwin" before setting
the `MallocNanoZone` envvar, but on the Shell lit config this attribute
does not exist at the point where it is being checked which leads to a
build failure.

This commit checks the host OS correctly.

Author: chelcassanova

lldb/test/API/lit.cfg.py

@@ -121,6 +121,7 @@ def delete_module_cache(path):
             config.environment["DYLD_INSERT_LIBRARIES"] = find_sanitizer_runtime(
                 "libclang_rt.asan_osx_dynamic.dylib"
             )
+            config.environment["MallocNanoZone"] = "0"
 
     if "Thread" in config.llvm_use_sanitizer:
         config.environment["TSAN_OPTIONS"] = "halt_on_error=1"

lldb/test/Shell/lit.cfg.py

@@ -52,6 +52,8 @@
 # Enable sanitizer runtime flags.
 config.environment["ASAN_OPTIONS"] = "detect_stack_use_after_return=1"
 config.environment["TSAN_OPTIONS"] = "halt_on_error=1"
+if platform.system() == "Darwin":
+    config.environment["MallocNanoZone"] = "0"
 
 # Support running the test suite under the lldb-repro wrapper. This makes it
 # possible to capture a test suite run and then rerun all the test from the