Allow standard tools to be overwritten in make invocation

diff --git a/Makefile b/Makefile
index 57e935174ce81242969ae2c86ef9114a62c1e31d..280c9d6a1172271f1c2e60d6281b5633d11f8141 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -57,9 +57,9 @@ CXXFLAGS += -Wall -Wextra -ggdb -I. -I"$(YOSYS_SRC)" -MD -D_YOSYS_ -fPIC -I$(PRE
 LDFLAGS += -L$(LIBDIR)
 LDLIBS = -lstdc++ -lm
 
-PKG_CONFIG = pkg-config
-SED = sed
-BISON = bison
+PKG_CONFIG ?= pkg-config
+SED ?= sed
+BISON ?= bison
 
 ifeq (Darwin,$(findstring Darwin,$(shell uname)))
        BREW := $(shell command -v brew 2> /dev/null)