fix syntax errors in configure script
diff --git a/configure b/configure
index 1b6b464..143dc92 100755
--- a/configure
+++ b/configure
@@ -421,7 +421,7 @@
tryflag CFLAGS_AUTO -Wno-pointer-to-int-cast
fi
-if test "x$visibility" == xauto ; then
+if test "x$visibility" = xauto ; then
# This test checks toolchain support for several things:
# - the -include option
# - the attributes/pragmas used in vis.h
@@ -441,7 +441,7 @@
printf "%s\n" "$visibility"
fi
-if test "x$visibility" == xyes ; then
+if test "x$visibility" = xyes ; then
CFLAGS_AUTO="$CFLAGS_AUTO -include vis.h"
CFLAGS_AUTO="${CFLAGS_AUTO# }"
fi