Create statically-linked Linux binaries on release (#1148)

Co-authored-by: Antonio Vivace <[email protected]>

Makefile

@@ -224,7 +224,7 @@ checkdiff:
 # The rationale for some of the flags is documented in the CMakeLists.
 
 develop:
-	$Qenv ${MAKE} WARNFLAGS="-Werror -Wextra \
+	$Qenv ${MAKE} WARNFLAGS="${WARNFLAGS} -Werror -Wextra \
 		-Walloc-zero -Wcast-align -Wcast-qual -Wduplicated-branches -Wduplicated-cond \
 		-Wfloat-equal -Wlogical-op -Wnull-dereference -Wshift-overflow=2 \
 		-Wstringop-overflow=4 -Wstrict-overflow=5 -Wundef -Wuninitialized -Wunused \