package/linux-headers: add comment to safely ignore missing cross-compiler

For some architectures (eg. Arc, Cris, Hexagon, ia64, Parisc, Score and
Xtensa), the Linux buildsystem tries to call the cross-compiler when
installing the headers.

This is a spurious call, since a cross-compiler is not needed at all to
install the headers.

As some users have reported the issue, just add a comment in linux-headers.mk
directing the user to ignore those errors.

Reported-by: Noam Camus <noamc@ezchip.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/linux-headers/linux-headers.mk

@@ -17,6 +17,12 @@ LINUX_HEADERS_SOURCE = linux-$(LINUX_HEADERS_VERSION).tar.xz
 
 LINUX_HEADERS_INSTALL_STAGING = YES
 
+# For some architectures (eg. Arc, Cris, Hexagon, ia64, parisc,
+# score and xtensa), the Linux buildsystem tries to call the
+# cross-compiler, although it is not needed at all.
+# This results in seemingly errors like:
+#   [...]/scripts/gcc-version.sh: line 26: arc-linux-uclibc-gcc: command not found
+# Those can be safely ignored.
 define LINUX_HEADERS_INSTALL_STAGING_CMDS
 	(cd $(@D); \
 		$(TARGET_MAKE_ENV) $(MAKE) \