soong: Add ability to build scudo-free 32-bit libc variant.

Targets can switch on this feature by setting
MALLOC_SVELTE_FOR_LIBC32 := true

The default is to build libc32 with scudo enabled.

Change-Id: I207659af05412a8e7dc850d57b491ee565554a65
diff --git a/core/soong_config.mk b/core/soong_config.mk
index 46598c0..d002398 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -154,6 +154,9 @@
 $(call add_json_str,  RecoverySnapshotVersion,           $(RECOVERY_SNAPSHOT_VERSION))
 $(call add_json_list, Platform_systemsdk_versions,       $(PLATFORM_SYSTEMSDK_VERSIONS))
 $(call add_json_bool, Malloc_low_memory,                 $(findstring true,$(MALLOC_SVELTE) $(MALLOC_LOW_MEMORY)))
+$(call add_json_bool, Malloc_low_memory_libc32,          $(if $(MALLOC_SVELTE_FOR_LIBC32),\
+                                                            $(filter true,$(MALLOC_SVELTE_FOR_LIBC32)),\
+                                                            $(findstring true,$(MALLOC_SVELTE) $(MALLOC_LOW_MEMORY))))
 $(call add_json_bool, Malloc_zero_contents,              $(call invert_bool,$(filter false,$(MALLOC_ZERO_CONTENTS))))
 $(call add_json_bool, Malloc_pattern_fill_contents,      $(MALLOC_PATTERN_FILL_CONTENTS))
 $(call add_json_str,  Override_rs_driver,                $(OVERRIDE_RS_DRIVER))