[test-suite] Suppress FP_CONTRACT due to command line changes planned in D74436
The dependent clang patch changes the default setting for ffp-contract to true,
and that causes about 20 test-suite LNT tests to fail on X86 and other arch.
This patch modifies the build settings to these tests to suppress FP_CONTRACT
and allows the tests to pass.
Reviewed By: andrew.kaylor, segpop, rengolin, jdoerfert
Differential Revision: https://reviews.llvm.org/D102861