`FetchContent` respects existing installs, and downloads and compiles the libs
if they aren't found.
This is admittedly a little finicky, since this ignores the usual `Find*`
modules provided by CMake, requiring a bit of glue on our side.
But, one upside is that this moves that logic from our CI into the build system,
which can thus benefit other downstream users.
This also opens the door to some improvements in upcoming commits.
Doing this with Bison turned out to be much more painful, however, due to
`FindBISON` providing the specific `bison_target` command; thus, it remains
installed externally, so that it can be picked up by `FindBISON`.
This also bumps our CMake version requirement slightly, though it's
possible that older versions keep working, or could be supported with small patches;
however, our CI doesn't provide anything below 3.31, so we can't check.
Note that the DLL name created by CMake with `BUILD_SHARED_LIBS`
has changed from `zlib1.dll` to `z.dll`. This was caused by the
"Continued rewrite of CMake build [Vollstrecker]" from its
changelog <https://zlib.net/ChangeLog.txt>, and has been reported
in <https://github.com/madler/zlib/issues/1181>.
The MinGW package `libz-mingw-w64-dev` still calls it `libz1.dll`.
fix#1157 for the following source code
```
section "hSAVE_locals",HRAM
func3.hSpam: ds 1 ; no longer produces an error
;.hEggs: ds 1 ; uncomment this to see the new error
section "demo",ROM0
func3:
ldh a, [.hSpam]
ret
```
Remove two errors:
- `Not currently in the scope of 'func3'`
- `Local label 'func3.hSpam' in main scope`
Add one error:
- `Relative local label '.hSpam' in main scope`
Co-authored-by: Rangi <35663410+Rangi42@users.noreply.github.com>
