guard ncp spinel tests with OPENTHREAD_BUILD_TESTS (#187)

src/ncp/Makefile.am

@@ -67,6 +67,8 @@ libopenthread_ncp_a_SOURCES         = \
 include_HEADERS                     = \
     $(NULL)
 
+if OPENTHREAD_BUILD_TESTS
+
 noinst_PROGRAMS                     = spinel-test
 spinel_test_SOURCES                 = spinel.c
 spinel_test_CFLAGS                  = -DSPINEL_SELF_TEST=1
@@ -78,5 +80,6 @@ install-headers: install-includeHEADERS
 if OPENTHREAD_BUILD_COVERAGE
 CLEANFILES                          = $(wildcard *.gcda *.gcno)
 endif # OPENTHREAD_BUILD_COVERAGE
+endif # OPENTHREAD_BUILD_TESTS
 
 include $(abs_top_nlbuild_autotools_dir)/automake/post.am

src/ncp/ncp_base.cpp

@@ -568,7 +568,7 @@ exit:
 void NcpBase::HandleCommandPropertySet(uint8_t header, spinel_prop_key_t key, const uint8_t *value_ptr,
                                        uint16_t value_len)
 {
-    int i;
+    unsigned i;
 
     if (mSending)
     {