Dont use _XOPEN_SOURCE when building

Apparently it has exactly opposite semantics for glibc and whatever libcs
are used on BSD. What a clusterfuck.

glfw/ibus_glfw.c

@@ -47,6 +47,20 @@ enum Capabilities {
     IBUS_CAP_SURROUNDING_TEXT   = 1 << 5
 };
 
+// implement strdup ourselves because the various unix/libc flavors all
+// require different sets of macros to make it available, and I cannot be
+// bothered
+static inline char*
+strdup(const char *src) {
+    size_t len = strlen(src);
+    char *ans = malloc(len + 1);
+    if (ans) {
+        memcpy(ans, src, len);
+        ans[len] = 0;
+    }
+    return ans;
+}
+
 
 static inline GLFWbool
 test_env_var(const char *name, const char *val) {

setup.py

@@ -181,7 +181,7 @@ def init_env(
     sanitize_args = get_sanitize_args(cc, ccver) if sanitize else set()
     cppflags = os.environ.get(
         'OVERRIDE_CPPFLAGS', (
-            '-D_XOPEN_SOURCE=700 -D{}DEBUG'
+            '-D{}DEBUG'
         ).format(
             ('' if debug else 'N'),
         )