Bug 1841902 - Patch ld64 to avoid dead-stripping rust compiler_builti…

…ns atoms. r=firefox-build-system-reviewers,ahochheiden

Sent upstream at tpoechtrager/cctools-port#135.

Differential Revision: https://phabricator.services.mozilla.com/D182833

taskcluster/scripts/misc/build-cctools-port.sh

@@ -68,6 +68,8 @@ export CXX="$CXX --sysroot=$MOZ_FETCHES_DIR/sysroot"
 
 # Configure crosstools-port
 cd $CROSSTOOLS_CCTOOLS_DIR
+patch -p2 < $GECKO_PATH/taskcluster/scripts/misc/cctools.patch
+
 # Force re-libtoolization to overwrite files with the new libtool bits.
 perl -pi -e 's/(LIBTOOLIZE -c)/\1 -f/' autogen.sh
 ./autogen.sh

taskcluster/scripts/misc/cctools.patch

@@ -0,0 +1,17 @@
+diff --git a/cctools/ld64/src/ld/Resolver.cpp b/cctools/ld64/src/ld/Resolver.cpp
+index bfb67a3..d5b1c67 100644
+--- a/cctools/ld64/src/ld/Resolver.cpp
++++ b/cctools/ld64/src/ld/Resolver.cpp
+@@ -1178,9 +1178,10 @@ void Resolver::deadStripOptimize(bool force)
+ 			// unset liveness, so markLive() will recurse
+ 			(const_cast<ld::Atom*>(atom))->setLive(0);
+ 		}
+-		// <rdar://problem/49468634> if doing LTO, mark all libclang_rt* mach-o atoms as live since the backend may suddenly codegen uses of them
++		// <rdar://problem/49468634> if doing LTO, mark all libclang_rt* mach-o atoms as live since the backend may suddenly codegen uses of them.
++		// Likewise with rust compiler_builtins atoms. They may come from a libcompiler_builtins-<hash>.a lib, or from a compiler_builtins-... member of a rust static library.
+ 		else if ( _haveLLVMObjs && !force && (atom->contentType() !=  ld::Atom::typeLTOtemporary) ) {
+-			if ( strstr(atom->safeFilePath(), "libclang_rt") != nullptr ) {
++			if ( strstr(atom->safeFilePath(), "libclang_rt") != nullptr || strstr(atom->safeFilePath(), "compiler_builtins") != nullptr ) {
+ 				_deadStripRoots.insert(atom);
+ 			}
+ 		}