[travis] add build checks for OT_LOG_LEVEL_NONE and OT_LOG_LEVEL_DEBG (#2076)

.travis/script.sh

@@ -196,8 +196,16 @@ set -x
 [ $BUILD_TARGET != posix ] || {
     sh -c '$CC --version' || die
     sh -c '$CXX --version' || die
+
+    git checkout -- . || die
+    git clean -xfd || die
     ./bootstrap || die
-    make -f examples/Makefile-posix || die
+    CPPFLAGS=-DOPENTHREAD_CONFIG_LOG_LEVEL=OT_LOG_LEVEL_NONE make -f examples/Makefile-posix || die
+
+    git checkout -- . || die
+    git clean -xfd || die
+    ./bootstrap || die
+    CPPFLAGS=-DOPENTHREAD_CONFIG_LOG_LEVEL=OT_LOG_LEVEL_DEBG make -f examples/Makefile-posix || die
 }
 
 [ $BUILD_TARGET != posix-distcheck ] || {

src/core/meshcop/dtls.cpp

@@ -488,6 +488,7 @@ void Dtls::HandleMbedtlsDebug(void *ctx, int level, const char *, int, const cha
 {
     Dtls *pThis = static_cast<Dtls *>(ctx);
     OT_UNUSED_VARIABLE(pThis);
+    OT_UNUSED_VARIABLE(str);
 
     switch (level)
     {