Linux: Recognize multiarch directories for musl-linux-any

When bootstrapping Debian for musl-linux-any, the multiarch directories
are not found due to an overly-specific regular expression.

See https://bugs.debian.org/1085507 for the original bug report.

Modules/Platform/Linux-Initialize.cmake

@@ -2,4 +2,4 @@ set(LINUX 1)
 set(UNIX 1)
 
 # Match multiarch library directory names.
-set(CMAKE_LIBRARY_ARCHITECTURE_REGEX "[a-z0-9_]+(-[a-z0-9_]+)?-linux-gnu[a-z0-9_]*")
+set(CMAKE_LIBRARY_ARCHITECTURE_REGEX "[a-z0-9_]+(-[a-z0-9_]+)?-linux-[a-z0-9_]*")