Fix build breakage on mips64 and x86_64.

It appears that mips64 doesn't define the same flags for handling long
doubles as the other target architectures. For x86_64, it is spuriously
seeing a request for floatditf(), which I have to narrow down. This
patch fixes the breakage for now, but should be cleaned up when more
appropriate fixes are available.

Change-Id: I3aeef46293bd6dd176096e0b92da714f61188068
(cherry picked from commit b3608ebad1c804ff31760e3a694f48c4bc9c88ed)
diff --git a/Android.mk b/Android.mk
index 35dbf6f..ac8a8ee 100644
--- a/Android.mk
+++ b/Android.mk
@@ -358,6 +358,7 @@
 
 LOCAL_MODULE := libcompiler_rt
 LOCAL_CFLAGS_arm += -D__ARM_EABI__
+LOCAL_CFLAGS_mips64 += -DCRT_HAS_128BIT -DCRT_LDBL_128BIT
 LOCAL_ASFLAGS := -integrated-as
 LOCAL_CLANG := true
 LOCAL_SRC_FILES_arm := $(call get-libcompiler-rt-source-files,arm)
@@ -366,6 +367,7 @@
 LOCAL_SRC_FILES_mips64 := $(call get-libcompiler-rt-source-files,mips64)
 LOCAL_SRC_FILES_x86 := $(call get-libcompiler-rt-source-files,x86)
 LOCAL_SRC_FILES_x86_64 := $(call get-libcompiler-rt-source-files,x86_64)
+LOCAL_SRC_FILES_x86_64 += lib/builtins/ppc/floatditf.c
 LOCAL_MODULE_TARGET_ARCH := arm arm64 mips mips64 x86 x86_64
 LOCAL_ADDITIONAL_DEPENDENCIES := $(LOCAL_PATH)/Android.mk
 LOCAL_ADDRESS_SANITIZER := false