The updated picolibc version has "isblank" function with external
linkage. This is required for C++ modules support.
This should solve all the problems reported in #76980, but
we'll wait to validate this with the modules build without
closing that issue.
Picolibc is a C Standard Library that is commonly used in embedded
environments. This patch adds initial support for this configuration
along with pre-commit CI. As of this patch, the test suite only builds
the tests and nothing is run. A follow-up patch will make the test suite
actually run the tests.
Differential Revision: https://reviews.llvm.org/D154246
