[NDK19] Remove --sysroot from LDFLAGS for cffi and pymunk (kivy#1965)

Because `--sysroot` flag is not needed anymore and make it fails the build since we migrated to new android's build system (implemented in NDK r19)

See also:
  - https://developer.android.com/ndk/guides/other_build_systems

Author: opacam

pythonforandroid/recipes/cffi/__init__.py

@@ -38,7 +38,6 @@ def get_recipe_env(self, arch=None):
         ndk_dir = self.ctx.ndk_platform
         ndk_lib_dir = os.path.join(ndk_dir, 'usr', 'lib')
         env['LDFLAGS'] += ' -L{}'.format(ndk_lib_dir)
-        env['LDFLAGS'] += " --sysroot={}".format(self.ctx.ndk_platform)
         env['PYTHONPATH'] = ':'.join([
             self.ctx.get_site_packages_dir(),
             env['BUILDLIB_PATH'],

pythonforandroid/recipes/pymunk/__init__.py

@@ -14,7 +14,6 @@ def get_recipe_env(self, arch):
         env['PYTHON_ROOT'] = self.ctx.get_python_install_dir()
         env['LDFLAGS'] += " -shared -llog"
         env['LDFLAGS'] += ' -L{}'.format(join(self.ctx.ndk_platform, 'usr', 'lib'))
-        env['LDFLAGS'] += " --sysroot={}".format(self.ctx.ndk_platform)
         env['LIBS'] = env.get('LIBS', '') + ' -landroid'
         return env