tools/nolibc: error out on unsupported architecture

When an architecture is unsupported arch.h would silently continue.
This leads to a lot of followup errors because my_syscallX() is not
defined and the startup code is missing.

Avoid these confusing errors and fail the build early with a clear
error message and location.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Willy Tarreau <w@1wt.eu>

tools/include/nolibc/arch.h

@@ -33,6 +33,8 @@
 #include "arch-s390.h"
 #elif defined(__loongarch__)
 #include "arch-loongarch.h"
+#else
+#error Unsupported Architecture
 #endif
 
 #endif /* _NOLIBC_ARCH_H */