cmake: build zlib manually in internal build

Separated from !1854 (merged).

The zlib CMakeLists.txt has a lot of errant effects on the build that can't be easily worked around, particularly with CTest. It's easier to just build it using the downloaded sources with our own script.

• Additionally makes openmpt not build with debug symbols because it blows up in size
• Additionally copies windows dlls to build/bin when building internal shared libraries for convenience
• Additionally adds /build to gitignore
• Additionally disables in-source builds

changed milestone to %2.2.11

added 3 commits

• f460e82b - cmake: link Rpcrt4 (for uuid) to openmpt on win32
• 4037d049 - cmake: copy build shared internal libs to bin/
• c1023b54 - cmake: disable debug symbols for openmpt

Compare with previous version

added 2 commits

• 54bfed1b - cmake: gitignore /build
• e265adf5 - cmake: disallow in-source builds

Compare with previous version

changed the description

merged

mentioned in commit 3597957a

mentioned in commit 12c2ddb1