Fix warnings reported by -Wpedantic

Previously CI hasn't been running with -Wpedantic (using autoconf), so
these haven't been reported previously.

- replace BUILD_ASSERT with static_assert()
- don't use %m GNU extension for printf
- don't use arithmetic on void*
- remove unused variables

Change-Id: I97d1acc908f06773b8b1ee95bfee80760fdc7a63
Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
diff --git a/tests/test_astlpc.c b/tests/test_astlpc.c
index e8f2bce..48beb4e 100644
--- a/tests/test_astlpc.c
+++ b/tests/test_astlpc.c
@@ -1515,20 +1515,13 @@
 };
 /* clang-format on */
 
-#ifndef BUILD_ASSERT
-#define BUILD_ASSERT(x)                                                        \
-	do {                                                                   \
-		(void)sizeof(char[0 - (!(x))]);                                \
-	} while (0)
-#endif
-
 int main(void)
 {
 	size_t i;
 
 	mctp_set_log_stdio(MCTP_LOG_DEBUG);
 
-	BUILD_ASSERT(ARRAY_SIZE(astlpc_tests) < SIZE_MAX);
+	static_assert(ARRAY_SIZE(astlpc_tests) < SIZE_MAX, "size");
 	for (i = 0; i < ARRAY_SIZE(astlpc_tests); i++) {
 		mctp_prlog(MCTP_LOG_DEBUG, "begin: %s", astlpc_tests[i].name);
 		astlpc_tests[i].test();
diff --git a/tests/test_core.c b/tests/test_core.c
index 435e5e4..ead3990 100644
--- a/tests/test_core.c
+++ b/tests/test_core.c
@@ -623,20 +623,13 @@
 };
 /* clang-format on */
 
-#ifndef BUILD_ASSERT
-#define BUILD_ASSERT(x)                                                        \
-	do {                                                                   \
-		(void)sizeof(char[0 - (!(x))]);                                \
-	} while (0)
-#endif
-
 int main(void)
 {
 	uint8_t i;
 
 	mctp_set_log_stdio(MCTP_LOG_DEBUG);
 
-	BUILD_ASSERT(ARRAY_SIZE(mctp_core_tests) < SIZE_MAX);
+	static_assert(ARRAY_SIZE(mctp_core_tests) < SIZE_MAX, "size");
 	for (i = 0; i < ARRAY_SIZE(mctp_core_tests); i++) {
 		mctp_prlog(MCTP_LOG_DEBUG, "begin: %s",
 			   mctp_core_tests[i].name);