SysrootStdModule runs over staged layouts that need no compiler: a
sysroot with its own module source, one on a point release of the
toolchain's libc++, one on the next major release with a shipped
source, one nothing was shipped for, one without libc++ at all, and the
two cases where a release cannot be read. The last block drives Build()
against a sysroot claiming libc++ 99 and expects the one-line
explanation back instead of compiler output, which is the failure the
fix replaces.
ToolchainResolve additionally checks that the release is read from the
libc++ the module source comes from (the prefix's, an explicit libc++
install's, the system's) and where the shipped sources are looked up.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Jorijn van der Graaf
cbf2b94f06