Added more warnings-as-errors flags

Added `-Werror=sign-compare -Werror=unused-variable -Werror=parentheses` to the
rhel8_gcc-8.5.0-serial Trilinos configuration.

These three warnings-as-errors flags serve as the starting steps to introduce
more warnings-as-errors flags going forward without overwhelming package developers
too much off the bat.

NOTE: Trilinos cannot currently enable `-Werror` due to how deprecated package
header warnings are implemented in PR trilinos#12828 (controlled by -Wcpp which is controls a lot of other
warnings).

Signed-off-by: Anderson <[email protected]>

packages/framework/ini-files/config-specs.ini

@@ -3110,7 +3110,7 @@ opt-set-cmake-var TPL_ENABLE_Scotch   BOOL FORCE : OFF
 opt-set-cmake-var TPL_Netcdf_LIBRARIES STRING FORCE : ${NETCDF_C_LIB|ENV}/libnetcdf.so
 
 opt-set-cmake-var Trilinos_ENABLE_Fortran OFF    BOOL         : OFF
-opt-set-cmake-var CMAKE_CXX_FLAGS                STRING       : -Wall -Wno-clobbered -Wno-vla -Wno-pragmas -Wno-unknown-pragmas -Wno-parentheses -Wno-unused-local-typedefs -Wno-literal-suffix -Wno-deprecated-declarations -Wno-misleading-indentation -Wno-int-in-bool-context -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-nonnull-compare -Wno-address -Wno-inline -Wno-unused-but-set-variable -Wno-unused-variable -Wno-unused-label -Werror=shadow -DTRILINOS_HIDE_DEPRECATED_HEADER_WARNINGS
+opt-set-cmake-var CMAKE_CXX_FLAGS STRING : -Wall -Wno-clobbered -Wno-vla -Wno-pragmas -Wno-unknown-pragmas -Wno-unused-local-typedefs -Wno-literal-suffix -Wno-deprecated-declarations -Wno-misleading-indentation -Wno-int-in-bool-context -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-nonnull-compare -Wno-address -Wno-inline -Wno-unused-label -Werror=parentheses -Werror=sign-compare -Werror=unused-variable -DTRILINOS_HIDE_DEPRECATED_HEADER_WARNINGS
 
 use GCC_PACKAGE_SPECIFIC_WARNING_FLAGS