Add a new `SWIFT_MODULE_NAME` property that defaults to the target name.
This is needed as otherwise, the first source file determines the module
name.
Issue: #18800
The swift compilation model requires all sources for the module to be
listed for the compiler to type check across them. Provide a
placeholder to allow enumerating the remainder of the swift sources in a
target for the language compile rule.
Issue: #18800
Add `CMAKE_SYSROOT_COMPILE` and `CMAKE_SYSROOT_LINK` variables to as
operation-specific alternatives to `CMAKE_SYSROOT`. This will be useful
for Android NDKs that compile and link with different sysroot values
(e.g. `r14` with unified headers).
Co-Author: Florent Castelli <florent.castelli@gmail.com>