[Buildroot] [PATCH v2] pkg-generic: error out with 'local' site method and no _SITE

[Arnout Vandecappelle (Essensium/Mind)]

The 'local' site method is easily confused with the 'file' site method,
making people create packages like this:

    FOO_SITE_METHOD = local
    FOO_SOURCE = foo.tar.gz

    $(eval $(generic-package))

Due to the intricacies of the generic package infra, this does not
cause an error; instead, the foo.tar.gz tarball that happens to be
present in the download directory will be used. This behaviour differs
greatly from what is specified in the manual.

Instead, error out immediately if a package specifies the 'local' site
method but does not specify a _SITE.

We check for _OVERRIDE_SRCDIR rather than checking for _SITE, just
after _OVERRIDE_SRCDIR has been set to _SITE. Indeed, a package that
sets _OVERRIDE_SRCDIR but not _SITE currently works correctly. There is
no reason to make it fail.

See also
https://stackoverflow.com/questions/50364655/including-patches-to-build-root

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout at mind.be>
---
v2: explain in commit message why we check for _OVERRIDE_SRCDIR
---
 package/pkg-generic.mk | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/package/pkg-generic.mk b/package/pkg-generic.mk
index 8a3b5f90a9..988f2d34e3 100644
--- a/package/pkg-generic.mk
+++ b/package/pkg-generic.mk
@@ -520,6 +520,9 @@ ifeq ($$($(2)_SITE_METHOD),local)
 ifeq ($$($(2)_OVERRIDE_SRCDIR),)
 $(2)_OVERRIDE_SRCDIR = $$($(2)_SITE)
 endif
+ifeq ($$($(2)_OVERRIDE_SRCDIR),)
+$$(error $(1) has local site method, but `$(2)_SITE_METHOD` is not defined)
+endif
 endif
 
 ifndef $(2)_LICENSE
-- 
2.17.0