Revert "Use ?:= as the assignement operator for PREFIX."

This reverts commit 59af25aafd51b706ed67784aa84332965c31bb26 as
it does not work with all versions of (gnu) make.

diff --git a/Makefile b/Makefile
index 78c9b1697b647cb6a56c9814ea2a94d8b86b8bdd..c61dff74c58533953951f105aaec1ce4c7965496 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -19,7 +19,7 @@ CPPFLAGS += -I/usr/local/include
 
 LDFLAGS += -L/usr/local/lib
 
-PREFIX ?:= /usr/local
+PREFIX ?= /usr/local
 ifeq "$(origin CC)" "default"
        CC := gcc
 endif