Fix issue for older versions of make

Apparently make 3.81 treats the following
```
define foo =
bar
baz
endef
```
differently than make 4.2.1 (most notably, the equals sign).

configure/E3/DEFINES_FT

 # Keep always the module up-to-date
-define git_update =
+define git_update
 rm -rf $(TOP)/$@
 git submodule init $@/
 git submodule update --init --recursive $@/.

require-ess/tools/driver.makefile

@@ -715,7 +715,7 @@ ${INSTALL_BINS}: $(addprefix ../,$(filter-out /%,${BINS})) $(filter /%,${BINS})
 	@echo "Installing binaries $^ to $(@D)"
 	$(INSTALL) -d -m$(BIN_PERMISSIONS) $^ $(@D)
 
-define license_install =
+define license_install
 $1: $2
 	@echo "Installing license file $$^"
 	$$(INSTALL) -d -m444 $$^ $$(@D)