test: Handle legacy stdio with atypical double format

When double is not 64 bits, the legacy stdio code doesn't work
correctly. This should probably just be disabled in the build script
somehow...

Author: keith-packard

test/printf_scanf.c

@@ -98,6 +98,10 @@
 # define NO_C99_FORMATS
 #endif
 
+#if __SIZEOF_DOUBLE__ != 8
+#define NO_FLOATING_POINT
+#endif
+
 #ifndef _WANT_IO_LONG_LONG
 #define NO_LONG_LONG
 #endif