Fixes strange C++11 compatibility problems during GTest installation:

 /tmp/gtest-20200216-20679-mu1044/googletest/include/gtest/internal/gtest-internal.h:1249:1: error: unknown type name 'constexpr'
 constexpr bool TypedTestCaseIsDeprecated() { return true; }

 /tmp/gtest-20200216-20679-mu1044/googletest/include/gtest/internal/gtest-internal.h:1249:11: error: expected unqualified-id
 constexpr bool TypedTestCaseIsDeprecated() { return true; }

 /tmp/gtest-20200216-20679-mu1044/googletest/include/gtest/internal/gtest-internal.h:1254:1: error: unknown type name 'constexpr'
 constexpr bool RegisterTypedTestCase_P_IsDeprecated() { return true; }

pip is bugged on arm64 and s390x. Add --no-cache-dir to fix. For
consistency, it doesn't hurt to add everywhere.

"The issue is that ParseCommandArgSignedSongTime parses with
SongTime::FromS, not SignedSongTime::FromS, before casting back to a
SignedSongTime for the return. With x86 overflow rules this doesn't
matter, but on ARM the first cast turns negative values to zero."

Closes https://github.com/MusicPlayerDaemon/MPD/issues/757

This is still needed for GTest 1.8.0 (Travis / Ubuntu Bionic).

Found with bugprone-suspicious-missing-comma
Signed-off-by: Rosen Penev <rosenp@gmail.com>

max_frames is size_t, not unsigned long. Fixes GCC warning.

When calling OggSeekFindEOS() from inside a OggVisitor callback, then
the #InputStream may be in the middle of an Ogg packet, and the newly
initialized #ogg_sync_state will not be able to load it without the
help of ogg_sync_pageseek().  By passing "synced=false" to
OggSeekFindEOS(), we force the use of ogg_sync_pageseek() even when
not actually seeking.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/719

Google Play refuses uploads with a lower targetSdkVersion.

Remove the error message and instead erase the old setting if the
"repeatable" flag is not set.

https://github.com/MusicPlayerDaemon/MPD/issues/684

By accident, this was only enabled for C.

This flag doesn't appear to work, and since we never had a problem
without the flag, implementing Google's recommendation is useless.

Don't export the symbols of all those static libraries.  Most
importantly, don't export the whole libc++ ABI.

These appear to be no longer necessary (tested with NDK r20b).

Closes https://github.com/android/ndk/issues/951

This implicitly defines __ANDROID_API__, which means we can drop the
"-D__ANDROID_API__=" parameter.

This is recommended on
https://android.googlesource.com/platform/ndk/+/ndk-release-r20/docs/BuildSystemMaintainers.md

It's not mentioned on
https://developer.android.com/ndk/guides/other_build_systems

Closes https://github.com/MusicPlayerDaemon/MPD/issues/708

It appears that [[fallthrough]] is valid in C++ but not in C. And
in some Clang versions (e.g. Clang 11 on macOS), Clang is pedantic
about this and considers it an error to use [[fallthrough]] in a
.c file such as src/util/format.c.

This changes makes gcc_fallthrough a no-op under Clang in C files.