Add 2 new tests that validate the ppc64le long double ABI
    
    This patch is highly based on the ppc64le-long-double test that was
    available in the previous commit.  However, it adds an extra step that
    ignores mock if the test is run inside an unprivileged container
    solution.
    
    The first test (exp) evaluates if clang is able to build C programs for
    both IBM double-double as well as IEEE 128-bit long double.  As Fedora uses
    glibc by default, which supports both scenarios, both executables should
    work.
    
    The second test (parse) uses clang in order to evaluate if C++ programs
    built with default parameters and linking against libc++ use IEEE
    128-bit long double.
    This test should be extended in the future in order to evaluate that
    clang is able to generate C++ programs for both IBM double-double and
    IEEE 128-bit long double using libstdc++.  This can't be enabled now
    because of https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81122 .