Try fixing picolibc

Author: ldionne

libcxx/test/libcxx/system_reserved_names.gen.py

@@ -11,6 +11,7 @@
 # provided macros (in other words, ensure that we push/pop correctly everywhere).
 
 # RUN: %{python} %s %{libcxx-dir}/utils
+# END.
 
 import sys
 
@@ -28,6 +29,9 @@
 {lit_header_restrictions.get(header, '')}
 {lit_header_undeprecations.get(header, '')}
 
+// This is required to detect the platform we're building for below.
+#include <__config>
+
 #define SYSTEM_RESERVED_NAME This name should not be used in libc++
 
 // libc++ does not use single-letter names as a matter of principle.