Added `LINKER=gold` default

Fortune for memfd_secret-shim's current commit: Half blessing − 半吉

Makefile

@@ -33,6 +33,9 @@ INCLUDE_PREFIX := $(PROJECT)/
 AR?=ar
 RANLIB?=ranlib
 
+# Linker to use
+LINKER?=gold
+
 # Use gcc-{ar,ranlib} when using gcc
 ifeq ($(CXX),g++)
 	AR:=gcc-ar
@@ -120,6 +123,11 @@ COMMON_FLAGS+=$(addsuffix =1,$(addprefix -DFEATURE_,$(__FEATURES)))
 #	COMMON_FLAGS+=-ffast-math
 #endif
 
+# Add linker
+ifneq ($(LINKER),)
+	COMMON_FLAGS+=-fuse-ld=$(LINKER)
+endif
+
 # Arch and optimisation
 ifneq ($(ARCH),)
 	OPT_FLAGS+= $(addprefix -march=,$(ARCH))