Added directory change during biglink

This seems to be necessary with the ndk 15 changes, otherwise some
object files can't be linked. It seems like this should be fixable
with an LDFLAG, but I can't any changes here that would have broken
it.

Author: inclement

pythonforandroid/build.py

@@ -666,12 +666,16 @@ def biglink(ctx, arch):
     info('target {}'.format(join(ctx.get_libs_dir(arch.arch),
                                  'libpymodules.so')))
     do_biglink = copylibs_function if ctx.copy_libs else biglink_function
-    do_biglink(
-        join(ctx.get_libs_dir(arch.arch), 'libpymodules.so'),
-        obj_dir.split(' '),
-        extra_link_dirs=[join(ctx.bootstrap.build_dir,
-                              'obj', 'local', arch.arch)],
-        env=env)
+
+    # Move to the directory containing crtstart_so.o and crtend_so.o
+    # This is necessary with newer NDKs? A gcc bug?
+    with current_directory(join(ctx.ndk_platform, 'usr', 'lib')):
+        do_biglink(
+            join(ctx.get_libs_dir(arch.arch), 'libpymodules.so'),
+            obj_dir.split(' '),
+            extra_link_dirs=[join(ctx.bootstrap.build_dir,
+                                'obj', 'local', arch.arch)],
+            env=env)
 
 
 def biglink_function(soname, objs_paths, extra_link_dirs=[], env=None):