[Buildroot] [git commit branch/2021.11.x] package/erlang-rebar: fix linking failure on shared library

[Peter Korsgaard]

commit: https://git.buildroot.net/buildroot/commit/?id=3c630f207bf527977150ef59659b8d0b573f26c3
branch: https://git.buildroot.net/buildroot/commit/?id=refs/heads/2021.11.x

Add patch to fix linking failure while creating shared library. As
explained in the patch itself, there is no specific variable for when we
link a shared library and rebar itself rely on the default LDFLAGS. Since
by default every CFLAGS is filled with -fPIC we need to make sure that
every LDFLAGS is the same, so not having any other *_LDFLAGS variable to
fille with -fPIC let's add it to the main LDFLAGS.

Fixes:
http://autobuild.buildroot.net/results/602/60296a48210e7ffc6bc9fa50ee586441a8957e85/

Signed-off-by: Giulio Benetti <giulio.benetti at benettiengineering.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998 at free.fr>
(cherry picked from commit b00c034fe58ad2ae87b2289e07912b6c10d19ee1)
Signed-off-by: Peter Korsgaard <peter at korsgaard.com>
---
 ...ort_compiler-add-fPIC-to-LDFLAGS-by-defau.patch | 35 ++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/package/erlang-rebar/0001-src-rebar_port_compiler-add-fPIC-to-LDFLAGS-by-defau.patch b/package/erlang-rebar/0001-src-rebar_port_compiler-add-fPIC-to-LDFLAGS-by-defau.patch
new file mode 100644
index 0000000000..a9c1670a1f
--- /dev/null
+++ b/package/erlang-rebar/0001-src-rebar_port_compiler-add-fPIC-to-LDFLAGS-by-defau.patch
@@ -0,0 +1,35 @@
+From 7f54d48ee5db037778ead310e0b8278f3fe70b41 Mon Sep 17 00:00:00 2001
+From: Giulio Benetti <giulio.benetti at benettiengineering.com>
+Date: Sun, 19 Dec 2021 07:52:55 +0100
+Subject: [PATCH] src/rebar_port_compiler: add -fPIC to LDFLAGS by default
+
+Since both DRV_CFLAGS and EXE_CFLAGS list -fPIC we need also the LDFLAGS
+to follow them. Unfortunately adding -fPIC only to DRV_LDFLAGS and
+EXE_LDFLAGS is not sufficient, since when linking as a library(.so) it
+doesn't take into account those variables. Since -fPIC is needed by default
+by any kind of linking, let's add it to the general -fPIC. Rebar seems to
+link libraries without taking into account any variable listed in:
+src/rebar_port_compiler.erl
+this after testing and tracing for every variable.
+
+Signed-off-by: Giulio Benetti <giulio.benetti at benettiengineering.com>
+---
+ src/rebar_port_compiler.erl | 2 ++
+ 1 file changed, 2 insertions(+)
+
+diff --git a/src/rebar_port_compiler.erl b/src/rebar_port_compiler.erl
+index 9679c80..bd08b21 100644
+--- a/src/rebar_port_compiler.erl
++++ b/src/rebar_port_compiler.erl
+@@ -645,6 +645,8 @@ default_env() ->
+      {"OBJCOPY", get_tool(Arch, "objcopy", "objcopy")},
+      {"OBJDUMP", get_tool(Arch, "objdump", "objdump")},
+ 
++     {"LDFLAGS", "-fPIC $LDFLAGS"},
++
+      {"DRV_CXX_TEMPLATE",
+       "$CXX -c $CXXFLAGS $DRV_CFLAGS $PORT_IN_FILES -o $PORT_OUT_FILE"},
+      {"DRV_CC_TEMPLATE",
+-- 
+2.25.1
+