Fix Catch2 compilation with Clang 13

Author: trflynn89

extern/catchorg/files.mk

@@ -67,4 +67,5 @@ SRC_$(d) := \
 
 CXXFLAGS_$(d) += \
     -Wno-float-equal \
-    -Wno-sign-conversion
+    -Wno-sign-conversion \
+    -Wno-unused-variable

extern/catchorg/flags.mk

@@ -3,4 +3,5 @@ CXXFLAGS_$(d) += \
     -DCATCH_CONFIG_PREFIX_ALL \
     -DCATCH_CONFIG_FAST_COMPILE \
     -DCATCH_CONFIG_ENABLE_OPTIONAL_STRINGMAKER \
-    -DCATCH_CONFIG_DEFAULT_REPORTER=\"libfly\"
+    -DCATCH_CONFIG_DEFAULT_REPORTER=\"libfly\" \
+    -DCATCH_CONFIG_NO_POSIX_SIGNALS