Woptim/quotes for specs

[adrienbernede]

In this PR I add single quotes around Spack specs to work around an issue in Spack with complex flags parsing.
(see spack/spack#31214).

This issue arise when using Spack newer than spack/spack@0c7fd9b.

There is one caveat: With this change the spec in CI should always use double quotes, and flag quotes should be protected:

-    SPEC: "~fortran %[email protected]+libcpp cxxflags='-stdlib=libc++ -DGTEST_HAS_CXXABI_H_=0' cflags='-DGTEST_HAS_CXXABI_H_=0'"
+    SPEC: "~fortran %[email protected]+libcpp cxxflags=\"-stdlib=libc++ -DGTEST_HAS_CXXABI_H_=0\" cflags=\"-DGTEST_HAS_CXXABI_H_=0\""

So this may be breaking for some projects, but easily fixable.

[adrienbernede]

Changes validated in Umpire, release notes updated accordingly.

[kennyweiss]

Thanks @adrienbernede !