This port needs a newer GCC to build, so add USES=compiler:c++11-lang
to fix build on GCC-based architectures.

Additionally, it tests for AVX support even if AVX option is off,
which breaks the build.

Explicitly disable AVX when AVX option is off. Since avxargs is used
by BLASLAPACK option, rename their avxags to blaslapackargs.

While here, pet portlint (whitespace).

PR: 234179
Submitted by: Piotr Kubaj
Approved by: maintainer