lib/ext2fs: don't warn about lack of getmntent on Windows

It is expected that Windows doesn't have getmntent(), so don't warn
about it.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/lib/ext2fs/Android.bp b/lib/ext2fs/Android.bp
index eb4482d..f5cbeec 100644
--- a/lib/ext2fs/Android.bp
+++ b/lib/ext2fs/Android.bp
@@ -121,7 +121,6 @@
             enabled: true,
             include_dirs: ["external/e2fsprogs/include/mingw"],
             cflags: [
-                "-Wno-error=cpp",
                 "-Wno-format",
                 "-Wno-unused-variable",
                 "-Wno-error=typedef-redefinition",
diff --git a/lib/ext2fs/ismounted.c b/lib/ext2fs/ismounted.c
index fe64e8b..8fc0b99 100644
--- a/lib/ext2fs/ismounted.c
+++ b/lib/ext2fs/ismounted.c
@@ -408,7 +408,7 @@
 #ifdef HAVE_GETMNTINFO
 		retval = check_getmntinfo(device, mount_flags, mtpt, mtlen);
 #else
-#ifdef __GNUC__
+#if defined(__GNUC__) && !defined(_WIN32)
  #warning "Can't use getmntent or getmntinfo to check for mounted filesystems!"
 #endif
 		*mount_flags = 0;