[libc] Fix warnings for freelist_heap_test/fuzz (#136634)

Fixes #122367

Author: mysterymath

libc/fuzzing/__support/CMakeLists.txt

@@ -30,7 +30,6 @@ if(LLVM_LIBC_FULL_BUILD AND NOT LIBC_TARGET_OS_IS_GPU)
   add_libc_fuzzer(
     freelist_heap_fuzz
     SRCS
-      fake_heap.s
       freelist_heap_fuzz.cpp
     DEPENDS
       libc.src.__support.freelist_heap

libc/fuzzing/__support/fake_heap.s

@@ -17,6 +17,15 @@
 #include "src/string/memory_utils/inline_memmove.h"
 #include "src/string/memory_utils/inline_memset.h"
 
+asm(R"(
+.globl _end, __llvm_libc_heap_limit
+
+.bss
+_end:
+  .fill 1024
+__llvm_libc_heap_limit:
+)";
+
 using LIBC_NAMESPACE::FreeListHeap;
 using LIBC_NAMESPACE::inline_memset;
 using LIBC_NAMESPACE::cpp::nullopt;

libc/fuzzing/__support/freelist_heap_fuzz.cpp

@@ -63,7 +63,6 @@ if(LLVM_LIBC_FULL_BUILD AND NOT LIBC_TARGET_OS_IS_GPU)
     SUITE
       libc-support-tests
     SRCS
-      fake_heap.s
       freelist_heap_test.cpp
     DEPENDS
       libc.src.__support.CPP.span

libc/test/src/__support/CMakeLists.txt

@@ -13,6 +13,15 @@
 #include "src/string/memcpy.h"
 #include "test/UnitTest/Test.h"
 
+asm(R"(
+.globl _end, __llvm_libc_heap_limit
+
+.bss
+_end:
+  .fill 1024
+__llvm_libc_heap_limit:
+)");
+
 using LIBC_NAMESPACE::Block;
 using LIBC_NAMESPACE::freelist_heap;
 using LIBC_NAMESPACE::FreeListHeap;