fix ct build with bash 5

make/crosstool.mk

@@ -66,6 +66,8 @@ CROSSTOOL-NG_TMP     = crosstool-ng.$(CROSSTOOL-NG_VER)
 CROSSTOOL-NG_SOURCE = crosstool-ng.$(CROSSTOOL-NG_VER)
 CROSSTOOL-NG_URL    = https://github.com/crosstool-ng
 
+CROSSTOOL-NG_PATCH  = crosstool-ng-bash-version.diff
+
 # crosstool for hd2 depends on gcc-linaro
 GCC-LINARO_VER    = 4.9-2017.01
 GCC-LINARO_SOURCE = gcc-linaro-$(GCC-LINARO_VER).tar.xz
@@ -90,7 +92,8 @@ $(CROSS_BASE)/arm/hd51: | $(BUILD_TMP)
 	get-git-source.sh $(CROSSTOOL-NG_URL)/$(CROSSTOOL-NG_SOURCE) $(ARCHIVE)/$(CROSSTOOL-NG_SOURCE)
 	$(CPDIR)/$(CROSSTOOL-NG_SOURCE)
 	$(CHDIR)/$(CROSSTOOL-NG_TMP); \
-		git checkout 1dbb06f2
+		git checkout 1dbb06f2; \
+		$(call apply_patches, $(CROSSTOOL-NG_PATCH))
 ifeq ($(BOXMODEL), $(filter $(BOXMODEL), hd2 hd51 bre2ze4k))
 	$(CHDIR)/$(CROSSTOOL-NG_TMP); \
 		cp -a $(PATCHES)/crosstool-ng/gcc/* patches/gcc/linaro-6.3-2017.02

patches/crosstool-ng-bash-version.patch

@@ -0,0 +1,13 @@
+diff --git a/configure.ac b/configure.ac
+index 869226c1..9fb78d2b 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -273,7 +273,7 @@ ACX_PROG_VERSION_REQ_STRICT([BASH_SHELL],
+     [GNU bash >= 3.1],
+     [bash],
+     [bash],
+-    ['^GNU bash, version (3\.[1-9]|4)'])
++    ['^GNU bash, version (3\.[1-9]|4|5)'])
+ 
+ # We need a awk that *is* GNU awk
+ ACX_PROG_VERSION_REQ_STRICT([AWK],