package/c-libraries: need linux-headers

Now that we check that a target package in the _DEPENDENCIES of another
package has to be enabled in config, all target packages must have a
kconfig symbol.

Add a Kconfig symbol for linux-headers, and select it from the packages
that depends on it (C libraries).

Also remove the now-misleading comments "for legal-info" from the C
libraries.

Fixes:
    http://autobuild.buildroot.org/results/2a9/2a9e5d27b34357819b44f573a834da1ba5079030/
    ... and numerous similar failures ...

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/glibc/Config.in

@@ -1,9 +1,9 @@
 if BR2_TOOLCHAIN_BUILDROOT_EGLIBC
 
-# For legal-info
 config BR2_PACKAGE_EGLIBC
 	bool
 	default y
+	select BR2_PACKAGE_LINUX_HEADERS
 
 choice
 	prompt "eglibc version"
@@ -25,10 +25,10 @@ endif
 
 if BR2_TOOLCHAIN_BUILDROOT_GLIBC
 
-# For legal-info
 config BR2_PACKAGE_GLIBC
 	bool
 	default y
+	select BR2_PACKAGE_LINUX_HEADERS
 
 choice
 	prompt "glibc version"

package/linux-headers/Config.in

@@ -0,0 +1,2 @@
+config BR2_PACKAGE_LINUX_HEADERS
+	bool

package/musl/Config.in

@@ -1,5 +1,5 @@
-# For legal-info
 config BR2_PACKAGE_MUSL
 	bool
 	depends on BR2_TOOLCHAIN_USES_MUSL
 	default y
+	select BR2_PACKAGE_LINUX_HEADERS

package/uclibc/Config.in

@@ -1,9 +1,9 @@
 if BR2_TOOLCHAIN_BUILDROOT_UCLIBC
 
-# For legal-info
 config BR2_PACKAGE_UCLIBC
 	bool
 	default y
+	select BR2_PACKAGE_LINUX_HEADERS
 
 comment "uClibc Options"
 

toolchain/toolchain-buildroot/Config.in

@@ -110,6 +110,7 @@ config BR2_TOOLCHAIN_BUILDROOT_LIBC
 	default "glibc"  if BR2_TOOLCHAIN_BUILDROOT_GLIBC
 	default "musl"	 if BR2_TOOLCHAIN_BUILDROOT_MUSL
 
+source "package/linux-headers/Config.in"
 source "package/uclibc/Config.in"
 source "package/glibc/Config.in"
 source "package/binutils/Config.in.host"