package/brltty: fix cross-compilation

brltty has a very inventive buildsystem, where it internall runs
./configure for the build machine In doing so, it generates a list
of make variables to define what the build machine supports, like
it does for the target.

However, the build variables are generated with a convoluted sed
script that scans the target list, and appends _FOR_BUILD to each
target variables. Then, both lists are included from the Makefile,
on the assumption that the build variables will not clash with the
target variables.

Where it gets interesting, is that that sed script considers the
variables names to match '[A-Za-z][A-Za-z0-9_]*'

And there we see why ATSPI2_PACKAGE does not match: it contains a
digit.

So, some build variables will inevitably override target ones.

Fix that by simply expanding the matching regexp to allow digits
in variable names.

Fixes:
    http://autobuild.buildroot.org/results/a37/a37782b3cfc1a96cc129db8fade20a36a7b2d470/
    http://autobuild.buildroot.org/results/97e/97edc6a47d2140968e84b409cdc960604e5896f2/

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Mario Lang <mlang@blind.guru>
Cc: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/brltty/0004-buildsys-fix-cross-compilation.patch

@@ -0,0 +1,41 @@
+From 088666535a045dae71bd2fcc6b3a1553023106ce Mon Sep 17 00:00:00 2001
+From: "Yann E. MORIN" <yann.morin.1998@free.fr>
+Date: Wed, 22 Aug 2018 10:10:19 +0200
+Subject: [PATCH] buildsys: fix cross-compilation
+
+Some identifiers for includes and libs paths may contain digit, e.g.
+X11_PACKAGE or ATSPI2_PACKAGE or GLIB2_PACKAGE...
+
+Also detect those identifiers when doing cros-compilation, so that the
+_FOR_BUILD variants are really created and do not clash with the target
+variants.
+
+Fixes:
+    http://autobuild.buildroot.org/results/a37/a37782b3cfc1a96cc129db8fade20a36a7b2d470/build-end.log
+    http://autobuild.buildroot.org/results/97e/97edc6a47d2140968e84b409cdc960604e5896f2/build-end.log
+    [...]
+
+Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
+---
+Upstram status: submitted
+https://github.com/brltty/brltty/pull/142
+---
+ mk4build | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/mk4build b/mk4build
+index db90c86a9..551283825 100755
+--- a/mk4build
++++ b/mk4build
+@@ -112,7 +112,7 @@ fi
+ 
+ sedScript="${outputName}.${sedExtension}"
+ sed -n -e '
+-s/^ *\([A-Za-z][A-Za-z_]*\) *=.*$/\1/
++s/^ *\([A-Za-z][A-Za-z0-9_]*\) *=.*$/\1/
+ t found
+ d
+ :found
+-- 
+2.14.1
+