Default to hiding libgcc symbols in each object.

Bug: http://b/24166967
Change-Id: I3dba264ae70a2e13b3edee7575139e86ef49be71

core/binary.mk

@@ -412,6 +412,17 @@ ifeq ($(my_allow_undefined_symbols),)
 endif
 endif
 
+# Target modules shouldn't re-export libgcc.a because we don't want other
+# binaries importing them when they should be getting their own copy of the
+# builtins.
+#
+# Unfortunately --exclude-libs always overrides all other attempts to make a
+# symbol visible, and libc needs to make sure some of these symbols are
+# available for binary compatibility, so libc needs a way to disable this.
+ifneq ($(strip $(LOCAL_NO_EXCLUDE_LIBS)),true)
+  my_ldflags += -Wl,--exclude-libs,libgcc.a
+endif
+
 ifeq (true,$(LOCAL_GROUP_STATIC_LIBRARIES))
 $(LOCAL_BUILT_MODULE): PRIVATE_GROUP_STATIC_LIBRARIES := true
 else

core/clear_vars.mk

@@ -190,6 +190,7 @@ LOCAL_SANITIZE_RECOVER:=
 LOCAL_DBUS_PROXY_PREFIX:=
 LOCAL_INIT_RC:=
 LOCAL_MODULE_HOST_OS:=
+LOCAL_NO_EXCLUDE_LIBS:=
 
 # arch specific variables
 LOCAL_SRC_FILES_$(TARGET_ARCH):=