toolchain: introduce BR2_TOOLCHAIN_HAS_SHADOW_PASSWORDS

Unfortunately, the official Blackfin toolchains are built without the
shadow password support, so our default Busybox configuration fails to
build.

Therefore, we introduce a new hidden knob
BR2_TOOLCHAIN_HAS_SHADOW_PASSWORDS, which is set to yes for Buildroot
internal toolchain, for toolchains generated by the Crosstool-NG
backend, for Glibc external toolchains and for Uclibc custom external
toolchains. It is left unset by the Blackfin toolchain profile.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

toolchain/Config.in

@@ -10,6 +10,7 @@ choice
 
 config BR2_TOOLCHAIN_BUILDROOT
 	bool "Buildroot toolchain"
+	select BR2_TOOLCHAIN_HAS_SHADOW_PASSWORDS
 
 config BR2_TOOLCHAIN_EXTERNAL
 	bool "External toolchain"
@@ -20,6 +21,7 @@ config BR2_TOOLCHAIN_EXTERNAL
 
 config BR2_TOOLCHAIN_CTNG
 	bool "Crosstool-NG toolchain"
+	select BR2_TOOLCHAIN_HAS_SHADOW_PASSWORDS
 	help
 	  Say 'y' if you want to generate the toolchain with crosstool-NG
 	  ( http://ymorin.is-a-geek.org/projects/crosstool )

toolchain/toolchain-common.in

@@ -29,6 +29,9 @@ config BR2_INSTALL_LIBSTDCPP
 config BR2_TOOLCHAIN_HAS_THREADS
 	bool
 
+config BR2_TOOLCHAIN_HAS_SHADOW_PASSWORDS
+	bool
+
 config BR2_ENABLE_LOCALE_PURGE
 	bool "Purge unwanted locales"
 	help

toolchain/toolchain-external/Config.in

@@ -220,6 +220,7 @@ config BR2_TOOLCHAIN_EXTERNAL_GLIBC
 	select BR2_ENABLE_LOCALE
 	select BR2_PROGRAM_INVOCATION
 	select BR2_TOOLCHAIN_HAS_THREADS
+	select BR2_TOOLCHAIN_HAS_SHADOW_PASSWORDS
 
 config BR2_TOOLCHAIN_EXTERNAL_UCLIBC
 	bool
@@ -233,6 +234,9 @@ choice
 config BR2_TOOLCHAIN_EXTERNAL_CUSTOM_UCLIBC
 	bool "uClibc"
 	select BR2_TOOLCHAIN_EXTERNAL_UCLIBC
+	# For the time being, we assume that all custom external
+	# toolchains have shadow password support.
+	select BR2_TOOLCHAIN_HAS_SHADOW_PASSWORDS
 
 config BR2_TOOLCHAIN_EXTERNAL_CUSTOM_GLIBC
 	bool "glibc"