f90_correct: fc30 and ls07 fail with LLVM 10 on OpenPOWER

[bryanpkc]

While testing Classic Flang with LLVM 10 (flang-compiler/classic-flang-llvm-project#1), @gklimowicz ran across two failures in check-clang on OpenPOWER. The first is in f90_correct/fc30. The second is in f90_correct/ls07. These failures do not occur on LLVM 10 x86_64 or aarch64.

They appear to be related to how LLVM 10 on Power is handling negative zeros during the computation of COMPLEX multiplies. The two tests fail when they generate -0.0 for the imaginary part of a COMPLEX number, when the test results are expecting 0.0.