adjust cext warning option

Author: qunaibit

graalpython/com.oracle.graal.python.cext/CMakeLists.txt

@@ -60,10 +60,11 @@ set(TARGET_LIBPYTHON "python-${LLVM_MODE}")
 # common variables and compile/link options (for all build targets)
 ######################################################################
 
-set(CFLAGS_WARNINGS -Wall -Werror -Wno-unused-function -Wno-unused-variable -Wno-unused-const-variable
+set(CFLAGS_WARNINGS -Wall -Werror,-Wunknown-warning-option -Wno-unused-function -Wno-unused-variable -Wno-unused-const-variable
                     -Wno-tautological-constant-out-of-range-compare   # fileutils.c: wchar_t > MAX_UNICODE is always false on Windows
                     -Wno-unused-but-set-variable                      # sqlite.c: BOOL bRc
                     -Wno-ignored-pragmas                              # sre.c: #pragma optimize("agtw", on)
+                    -Wno-discarded-qualifiers                         # longobject.c: *pend = str; (gcc only hence: '-Wunknown-warning-option')
                     -Wno-int-to-pointer-cast -Wno-int-conversion -Wno-void-pointer-to-int-cast
                     -Wno-incompatible-pointer-types-discards-qualifiers -Wno-pointer-type-mismatch
                     -Wno-braced-scalar-init -Wno-deprecated-declarations)