CMakeParseLibraryArchitecture: Fix parsing /lib/<arch> implicit object path
The current regular expression is able to match `/usr/lib/<arch>`,
`/usr/usr/lib/<arch>`, `/usr/usr/usr/lib/<arch>`, ... but not
`/lib/<arch>`.
This behavior ends up causing the detected architecture to
be x86_64-pc-linux-gnu when the Clang compiler is installed on
a "non-system" location (like /opt/llvm-13) which, in turn, makes
almost every 'find_library()' fail because the correct
architecture is x86_64-linux-gnu.
This is due to a typo in commit 764606e256 (CMakeDetermineCompilerABI:
Extract lib arch from implicit object file paths, 2021-04-05,
v3.20.1~10^2), which used `+` instead of `?`.
9 files changed
