Fix windows support

Author: isuruf

setup.py

@@ -8,16 +8,12 @@
 
 from distutils.sysconfig import get_config_vars
 
-(opt,) = get_config_vars('OPT')
-os.environ['OPT'] = " ".join(flag for flag in opt.split() if flag != '-Wstrict-prototypes')
-
 if sys.platform == 'win32':
     libraries = ["flint", "arb", "mpir", "mpfr", "pthreads"]
-    default_lib_dirs += [
-        os.path.join(d, "manual-link") for d in default_lib_dirs
-    ]
 else:
     libraries = ["flint", "arb"]
+    (opt,) = get_config_vars('OPT')
+    os.environ['OPT'] = " ".join(flag for flag in opt.split() if flag != '-Wstrict-prototypes')
 
 default_include_dirs += [
     os.path.join(d, "flint") for d in default_include_dirs