(ppc64) Downport of 8170153 breaks build on linux/ppc64 (big endian)

The downport of "8170153: PPC64/s390x/aarch64: Poor StrictMath performance due to non-optimized compilation" to jdk8u breaks the build on linux/ppc64 (big endian) with the original compiler used to compile jdk8u on linux/ppc64.

JDK-8170153 increased the optimization level for the compilation of fdlibm on both linux/ppc64 and linux/ppc64le. This only worked by using the option '-ffp-contract=off' which guaranteed correct IEEE floating point behaviour.

Unfortunately, '-ffp-contract' is only available since gcc 4.6. For ppc64le that's no problem since ppc64le support only appeared in gcc 4.8.3. But on ppc64 (big endian) we traditionally compiled with gcc 4.3 which only knows '-mno-fused-madd'. However, that's still not enough to get the float computations right - we additionally have to supply '-fno-strict-aliasing'.

We should ensure that Linux distributions are able to build update releases of jdk8 with the original version of gcc (4.3 in this case).