Support compiling without PCRE (#12)

README.md

@@ -124,6 +124,12 @@ it comes to support.
 
 `make USE_SYSTEM_NIM=1 test`
 
+### LINK_PCRE
+
+Link PCRE, defaults to 1.
+
+`make LINK_PCRE=0`
+
 ## Make targets
 
 ### build

makefiles/variables.mk

@@ -32,11 +32,14 @@ ifdef LOG_LEVEL
 endif
 
 # avoid a "libpcre.so.3: cannot open shared object file: No such file or directory" message, where possible
+LINK_PCRE := 1
+ifeq ($(LINK_PCRE), 1)
   ifneq ($(OS), Windows_NT)
 	ifneq ($(strip $(shell uname)), Darwin)
 	  NIM_PARAMS := $(NIM_PARAMS) -d:usePcreHeader --passL:\"-lpcre\"
 	endif
   endif
+endif
 
 # guess who does parsing before variable expansion
 COMMA := ,