Added `TARGET` var for `test` - {debug,release}.{a,so} (which build of lib to link to,) and configurable `TEST_{C,LD}FLAGS`. Fixed bug of adding test flags to dep build when it doesn"t already exist.

Fortune for memfd_secret-shim's current commit: Blessing − 吉

Makefile

@@ -49,6 +49,13 @@ FEATURES?=
 # Build constants
 CONSTANTS+=_GNU_SOURCE
 
+# Testing 
+# Can be {release,debug}.{a,so}
+TARGET?=debug.a
+
+TEST_LDFLAGS+= -lfmt -lstdc++ -Wl,-z,now -Wl,-z -Wl,relro
+TEST_CFLAGS+= -Og -g -fwhole-program
+
 override __COMMA=,
 override __VERSION_SPLIT:= $(subst ., ,$(VERSION))
 override __VERSION_REVISION:=$(word 3,$(__VERSION_SPLIT)) 0
@@ -354,7 +361,5 @@ uninstall:
 		rmdir $(DESTDIR)$(PREFIX)/include/$(INCLUDE_PREFIX) || :
 
 #TODO: We can make the target between `{debug,release}{.a,.so}` configurable by call. e.g. `TARGET=release.a make test`
-$(PROJECT)-test: LDFLAGS+= -lfmt -lstdc++
-$(PROJECT)-test: CFLAGS+= -Og -g
-$(PROJECT)-test: lib$(PROJECT)-debug.a
-	$(CC) $(CFLAGS) -fwhole-program src/test/*.c -o $@ -l:$< $(LDFLAGS)
+$(PROJECT)-test: lib$(PROJECT)-$(TARGET)
+	$(CC) $(CFLAGS) $(TEST_CFLAGS) src/test/*.c -o $@ -l:$< $(LDFLAGS) $(TEST_LDFLAGS)