all.sh: build with -O -Werror in the full config

Build with MBEDTLS_DEPRECATED_REMOVED and MBEDTLS_DEPRECATED_WARNING
separately.

Do these builds with `-O -Werror -Wall -Wextra` to catch a maximum of
issues while we're at it. Do one with gcc and one with clang for
variety. This caught an uninitialized variable warning in cmac.c that
builds without -O didn't catch.

tests/scripts/all.sh

@@ -547,11 +547,23 @@ if_build_succeeded tests/ssl-opt.sh -f Default
 msg "test: compat.sh RC4, DES & NULL (full config)" # ~ 2 min
 if_build_succeeded env OPENSSL_CMD="$OPENSSL_LEGACY" GNUTLS_CLI="$GNUTLS_LEGACY_CLI" GNUTLS_SERV="$GNUTLS_LEGACY_SERV" tests/compat.sh -e '3DES\|DES-CBC3' -f 'NULL\|DES\|RC4\|ARCFOUR'
 
-msg "build: cmake, full config + DEPRECATED_REMOVED, clang, C99"
+msg "build: make, full config + DEPRECATED_WARNING, gcc -O" # ~ 30s
-# No cleanup: tweak the configuration, keep the makefiles
+cleanup
+cp "$CONFIG_H" "$CONFIG_BAK"
+scripts/config.pl full
 scripts/config.pl set MBEDTLS_DEPRECATED_WARNING
+# Build with -O -Wextra to catch a maximum of issues.
+make CC=gcc CFLAGS='-O -Werror -Wall -Wextra' lib programs
+make CC=gcc CFLAGS='-O -Werror -Wall -Wextra -Wno-unused-function' tests
+
+msg "build: make, full config + DEPRECATED_REMOVED, clang -O" # ~ 30s
+# No cleanup, just tweak the configuration and rebuild
+make clean
+scripts/config.pl unset MBEDTLS_DEPRECATED_WARNING
 scripts/config.pl set MBEDTLS_DEPRECATED_REMOVED
-make
+# Build with -O -Wextra to catch a maximum of issues.
+make CC=clang CFLAGS='-O -Werror -Wall -Wextra' lib programs
+make CC=clang CFLAGS='-O -Werror -Wall -Wextra -Wno-unused-function' tests
 
 msg "test/build: curves.pl (gcc)" # ~ 4 min
 cleanup