[libc] Display assertion failure message before incrementing counter

During early initialisation on some platforms, the .data and .bss
sections may not yet be writable.

Display the assertion message before attempting to increment the
assertion failure counter, since writing to the assertion counter may
trigger a CPU exception that ends up resetting the system.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/assert.h

@@ -49,9 +49,9 @@ assert_printf ( const char *fmt, ... ) asm ( "printf" );
 #define assert( condition ) 						     \
 	do { 								     \
 		if ( ASSERTING && ! (condition) ) { 			     \
-			assertion_failures++;				     \
 			assert_printf ( "assert(%s) failed at %s line %d\n", \
 					#condition, __FILE__, __LINE__ );    \
+			assertion_failures++;				     \
 		} 							     \
 	} while ( 0 )