libm: Support -ffp-contract=fast

Change-Id: I50d62cde33201c80837e6a97ce3708c96ed09021
Signed-off-by: HanyanI <yuhan@rsyhan.me>
Signed-off-by: Akash Srivastava <akashniki@gmail.com>
Signed-off-by: DennySPb <dennyspb@gmail.com>
Signed-off-by: Adithya R <gh0strider.2k18.reborn@gmail.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>

Author: dkati

libm/Android.bp

@@ -398,6 +398,7 @@ cc_library {
         "-Wno-unknown-pragmas",
         "-Wno-unused-const-variable",
         "-Wno-unused-variable",
+        "-ffp-contract=fast",
     ],
 
     ldflags: [