As of CMake 3.25, there are now global variables `LINUX=1`, `ANDROID=1`,
etc. These conflict with expressions that used these names as unquoted
strings in positions where CMake accepts 'variable|string', for example:
- `if(sdk STREQUAL LINUX)` would fail, because `LINUX` is now defined and
expands to 1, where it would previously coerce to a string.
- `if(${sdk} STREQUAL "LINUX")` would fail if `sdk=LINUX`, because the
left-hand side expands twice.
In this patch, I looked for a number of patterns to fix up, sometimes a
little defensively:
- Quoted right-hand side of `STREQUAL` where I was confident it was
intended to be a string literal.
- Removed manual variable expansion on left-hand side of `STREQUAL`,
`MATCHES` and `IN_LIST` where I was confident it was unintended.
Fixes#65028.
This moves `libstdcxx.modulemap` and `libstdcxx.h` from `*.xctoolchain/usr/lib/swift/macosx/arm64e` to `*.xctoolchain/usr/lib/swift/macosx` to simplify distribution.
rdar://110788977
