Use compiler builtins for fabs.

Change-Id: Id3bf761d6dfc187f218b5215c53d76bddc83d50b
diff --git a/libm/Android.mk b/libm/Android.mk
index 7b28f70..2d55b1d 100644
--- a/libm/Android.mk
+++ b/libm/Android.mk
@@ -108,8 +108,6 @@
     upstream-freebsd/lib/msun/src/s_exp2.c \
     upstream-freebsd/lib/msun/src/s_exp2f.c \
     upstream-freebsd/lib/msun/src/s_expm1f.c \
-    upstream-freebsd/lib/msun/src/s_fabs.c \
-    upstream-freebsd/lib/msun/src/s_fabsf.c \
     upstream-freebsd/lib/msun/src/s_fdim.c \
     upstream-freebsd/lib/msun/src/s_finite.c \
     upstream-freebsd/lib/msun/src/s_finitef.c \
@@ -175,7 +173,6 @@
     upstream-freebsd/lib/msun/src/s_copysignl.c \
     upstream-freebsd/lib/msun/src/e_coshl.c \
     upstream-freebsd/lib/msun/src/s_cosl.c \
-    upstream-freebsd/lib/msun/src/s_fabsl.c \
     upstream-freebsd/lib/msun/src/s_floorl.c \
     upstream-freebsd/lib/msun/src/s_fmal.c \
     upstream-freebsd/lib/msun/src/s_fmaxl.c \
@@ -228,6 +225,10 @@
 LOCAL_SRC_FILES += \
     signbit.c \
 
+# Home-grown stuff.
+LOCAL_SRC_FILES += \
+    fabs.cpp \
+
 # Arch specific optimizations.
 
 # -----------------------------------------------------------------------------