* Lower limit from API 21 to API 19
This was requested by an internal application. API 19 is when OpenGL
ES 3.0 support was added so there is no good reason for us to not
support this API level. The only trick is to avoid referring to the
glTexStorage2DMultisample symbol directly as it only exists in 3.1.
* Compile out code we never use
* Use reflection to handle shared EGL contexts pre-API 21.
* Remove comment
* More fixes required to run on API level 19
- dlym() fails for ashmem on API 19, so we only try on API 26+ instead.
- Older emulation for OpenGL ES 3.0 returns error states for valid API calls so we need to clear the GL error bit before we create the GL driver.
- Activity lifecycle changes since API 19 would cause animations to keep running and to reference destroyed objects.
- EGLContext.getNativeHandle() is new in API 21, we need to use reflection on API 19. The new code path uses the class loading trick to avoid a bytecode verification error on API 19.
* Filament now runs properly on API level 19
This commit adds a new api_level() API to libutils which can be used to
query the platform's API level. On Android it works as expected, other
platforms currently return 0.
This includes a small change to our custom material task because old
gradle passed only the contents of out-of-date directories, newer gradle
passes both the contents and the directory itself.
Filamat public headers were including a private header. This PR fixes
this problem. It also forces filamat to always be compiled to avoid
breaking filamat without noticing. The flag `-l` is not available
anymore in build.sh as a result.
