[Buildroot] [RFC PATCH v2] Handle _LICENSE_FILES with full path

[Cyril Bur]

legal-info currently assumes that a packages _LICENSE_FILES will be a
path or a filename relative to the source of the package.

There is nothing preventing _LICENSE_FILES from containing a full path.
When this happens, the legal-info process adds the build directory on
the front of the _LICENSE_FILES value resulting in a failed cp of the
file.

This patch adds a check to see if the _LICENSE_FILES path with the build
directory prepended exists (as is the case for all packages currently)
and uses that. Otherwise it will assume that the _LICENSE_FILES file is
a full path.

An 'offending' package .mk file could look something like this:
LIBFOO_VERSION = 1.0
LIBFOO_SOURCE = libfoo-$(LIBFOO_VERSION).tar.gz
LIBFOO_SITE = http://www.foosoftware.org/download
LIBFOO_LICENSE = GPL-3.0+
LIBFOO_LICENSE_FILES = $(LIBFOO_PKGDIR)/COPYING

[...]

$(eval $(generic-package))

Signed-off-by: Cyril Bur <cyrilbur at gmail.com>
---
Adding a licence file to buildroot is probably odd and a strange thing
to do, we're doing this internally (and I do hope I can push the package
soon) with https://github.com/BrianGladman/modes

V1->V2 Reworked commit message and added example as requested by Thomas
       Petazzoni
 package/pkg-generic.mk | 2 +-
 package/pkg-utils.mk   | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/package/pkg-generic.mk b/package/pkg-generic.mk
index ded5176428..e6d9f457e4 100644
--- a/package/pkg-generic.mk
+++ b/package/pkg-generic.mk
@@ -1139,7 +1139,7 @@ ifneq ($$(call qstrip,$$($(2)_SOURCE)),)
 ifeq ($$(call qstrip,$$($(2)_LICENSE_FILES)),)
 	$(Q)$$(call legal-warning-pkg,$$($(2)_BASENAME_RAW),cannot save license ($(2)_LICENSE_FILES not defined))
 else
-	$(Q)$$(foreach F,$$($(2)_LICENSE_FILES),$$(call legal-license-file,$$($(2)_RAWNAME),$$($(2)_BASENAME_RAW),$$($(2)_HASH_FILE),$$(F),$$($(2)_DIR)/$$(F),$$(call UPPERCASE,$(4)))$$(sep))
+	$(Q)$$(foreach F,$$($(2)_LICENSE_FILES),$$(call legal-license-file,$$($(2)_RAWNAME),$$($(2)_BASENAME_RAW),$$($(2)_HASH_FILE),$$(F),$$(call prefix-if-needed,$$($(2)_DIR),$$(F)),$$(call UPPERCASE,$(4)))$$(sep))
 endif # license files
 
 ifeq ($$($(2)_SITE_METHOD),local)
diff --git a/package/pkg-utils.mk b/package/pkg-utils.mk
index ae3c7f9da9..0c287a0f50 100644
--- a/package/pkg-utils.mk
+++ b/package/pkg-utils.mk
@@ -207,6 +207,10 @@ endif
 #
 LEGAL_INFO_SEPARATOR = "::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::"
 
+define prefix-if-needed # builddir, filename
+	$(if $(wildcard $(1)/$(2)),$(1)/$(2),$(2))
+endef
+
 define legal-warning # text
 	echo "WARNING: $(1)" >>$(LEGAL_WARNINGS)
 endef
-- 
2.34.0