build: stubgss tidy-ups (in tests)

- cmake: avoid running clang-tidy twice.
- autotools: do not pass curl/libtest-specific macros.

Also:
- autotools: drop `CFLAG_CURL_SYMBOL_HIDING` from libtests.
   Unused since 09437d8cd4 #14695

Closes #17738

tests/libtest/CMakeLists.txt

@@ -60,7 +60,7 @@ set_property(TARGET ${BUNDLE} APPEND PROPERTY COMPILE_DEFINITIONS "${CURL_DEBUG_
 set_property(TARGET ${BUNDLE} APPEND PROPERTY COMPILE_DEFINITIONS "CURL_NO_OLDIES" "CURL_DISABLE_DEPRECATION")
 set_target_properties(${BUNDLE} PROPERTIES OUTPUT_NAME "${BUNDLE}" PROJECT_LABEL "Test ${BUNDLE}" UNITY_BUILD OFF C_CLANG_TIDY "")
 
-curl_clang_tidy_tests(${BUNDLE} ${FIRSTFILES} ${UTILS} ${TESTFILES} ${STUB_GSS})
+curl_clang_tidy_tests(${BUNDLE} ${FIRSTFILES} ${UTILS} ${TESTFILES})
 
 if(HAVE_GSSAPI AND UNIX)
   add_library(stubgss SHARED EXCLUDE_FROM_ALL ${STUB_GSS})

tests/libtest/Makefile.am

@@ -45,8 +45,6 @@ include Makefile.inc
 EXTRA_DIST = CMakeLists.txt .checksrc $(FIRSTFILES) $(UTILS) $(TESTFILES) \
   test307.pl test610.pl test613.pl test1013.pl test1022.pl mk-lib1521.pl
 
-CFLAG_CURL_SYMBOL_HIDING = @CFLAG_CURL_SYMBOL_HIDING@
-
 CFLAGS += @CURL_CFLAG_EXTRAS@
 
 # Prevent LIBS from being used for all link targets
@@ -72,7 +70,7 @@ AM_CFLAGS =
 if BUILD_STUB_GSS
 noinst_LTLIBRARIES += libstubgss.la
 
-libstubgss_la_CPPFLAGS = $(AM_CPPFLAGS)
+libstubgss_la_CPPFLAGS =
 libstubgss_la_LDFLAGS = $(AM_LDFLAGS) -avoid-version -rpath /nowhere
 if CURL_LT_SHLIB_USE_NO_UNDEFINED
 libstubgss_la_LDFLAGS += -no-undefined