Use ECM's toolchain file

It works.
- If we use the one from CMake it doesn't look for libc.so file into the
ndk.
- If we use the one from Android it insists on looking for libraries
  only within the ndk.
Status Job ID Name Coverage
  Build
passed #1932697
build

00:03:44

failed #1932702
build_android

00:01:45

passed #1932698
build_clang_libcpp

00:04:47

passed #1932701
build_clazy

00:02:49

passed #1932700
build_mingw64_fedora

00:02:53

passed #1932699
build_ubuntu_16_04

00:01:57

 
Name Stage Failure
failed
build_android Build
../splash/SplashFTFontFile.cc:61: error: undefined reference to 'FT_Get_Name_Index'
../splash/SplashFTFontFile.cc:79: error: undefined reference to 'FT_New_Face'
../splash/SplashFTFontFile.cc:82: error: undefined reference to 'FT_New_Memory_Face'
../splash/SplashFTFontFile.cc:99: error: undefined reference to 'FT_New_Face'
../splash/SplashFTFontFile.cc:102: error: undefined reference to 'FT_New_Memory_Face'
../splash/SplashFTFontFile.cc:128: error: undefined reference to 'FT_Done_Face'
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.
ERROR: Job failed: exit code 1