[libc][stdlib] Fix skipped libc.src.stdlib.freelist_malloc target for baremetal. (#96372)

Downstream build issue reported:
https://ci.chromium.org/ui/p/fuchsia/builders/toolchain.ci/clang-linux-x64/b8744479865106393873/overview

Author: lntue

libc/config/baremetal/arm/entrypoints.txt

@@ -176,6 +176,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdlib.calloc
     libc.src.stdlib.div
     libc.src.stdlib.free
+    libc.src.stdlib.freelist_malloc
     libc.src.stdlib.labs
     libc.src.stdlib.ldiv
     libc.src.stdlib.llabs

libc/config/baremetal/riscv/entrypoints.txt

@@ -172,6 +172,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdlib.calloc
     libc.src.stdlib.div
     libc.src.stdlib.free
+    libc.src.stdlib.freelist_malloc
     libc.src.stdlib.labs
     libc.src.stdlib.ldiv
     libc.src.stdlib.llabs

libc/src/stdlib/CMakeLists.txt

@@ -392,7 +392,8 @@ else()
     COMPILE_OPTIONS
       -DLIBC_FREELIST_MALLOC_SIZE=${LIBC_CONF_FREELIST_MALLOC_BUFFER_SIZE}
   )
-  if(LIBC_TARGET_OS_IS_BAREMETAL)
+  get_target_property(freelist_malloc_is_skipped libc.src.stdlib.freelist_malloc "SKIPPED")
+  if(LIBC_TARGET_OS_IS_BAREMETAL AND NOT freelist_malloc_is_skipped)
     add_entrypoint_object(
       malloc
       ALIAS