If ScanLibDirForGCCTriple with target triple fail, let's try the triple
with vendor stripped if vendor is unknown.
Debian always uses triples without vendor section. In general,
triples without vendor section is the most similar aliases than any other
aliases.
To archive this, we add a private member TripleNoVendor to GCCInstallationDetector.
This modification makes testcase riscv32-toolchain.c and
riscv64-toolchain.c fails. And the real reason is that they are wrong:
--triple riscv64-unknown-elf tries to use riscv64-unknown-linux-gnu
first.
This patch accidentally fixes this problem.
We also drop the path delimiter pattern {{/|\\\\}}, as these 2 tests
are disabled on Windows, and in fact the positions of this pattern are
not correct.