Revert "Strip -fPIC compiler flag during compilation (#10209)"

Now that we have landed (for the third time) the binaryen fix for
WebAssembly/binaryen#2180 we can once
again allow `-fPIC` at compile time as an alternative to MAIN_MODULE
or SIDE_MODULE.

This reverts commit 19a9e35.

Author: sbc100

Diff for: emcc.py

@@ -1967,9 +1967,6 @@ def is_link_flag(flag):
         return any(flag.startswith(x) for x in ('-l', '-L', '-Wl,'))
 
       compile_args = [a for a in newargs if a and not is_link_flag(a)]
-      if '-fPIC' in compile_args and not shared.Settings.RELOCATABLE:
-        shared.warning('ignoring -fPIC flag when not building with SIDE_MODULE or MAIN_MODULE')
-        compile_args.remove('-fPIC')
 
       # Bitcode args generation code
       def get_clang_command(input_files):

Diff for: tests/test_core.py

@@ -8593,7 +8593,6 @@ def test_undefined_main(self):
 
   def test_fpic_static(self):
     self.emcc_args.append('-fPIC')
-    self.emcc_args.remove('-Werror')
     self.do_run_in_out_file_test('tests', 'core', 'test_hello_world')
 
   @node_pthreads