[PATCH] src/drivers/drivers.mak: add -D_GNU_SOURCE for libnl-tiny

[Ivan Ivanov]

[PATCH] src/drivers/drivers.mak: add -D_GNU_SOURCE for libnl-tiny

When building wpa_supplicant with some toolchains like musl libc
(e.g., from musl.cc project) and using libnl-tiny, compilation
fails because 'struct ucred' in netlink/msg.h is incomplete.
In musl, this structure is defined in sys/socket.h only inside an
"#ifdef _GNU_SOURCE" block, so the definition is hidden unless
_GNU_SOURCE is defined. Add -D_GNU_SOURCE to DRV_CFLAGS within the
CONFIG_LIBNL_TINY block to make the structure visible. This flag
is safe for other configurations and resolves errors such as:

  error: field 'nm_creds' has incomplete type
  error: invalid application of 'sizeof' to incomplete type 'struct ucred'

Signed off by: Ivan Ivanov <qmastery16 at gmail.com>

diff --git a/src/drivers/drivers.mak b/src/drivers/drivers.mak
index 5c819269f..160b53789 100644
--- a/src/drivers/drivers.mak
+++ b/src/drivers/drivers.mak
@@ -174,6 +174,7 @@ else
   ifdef CONFIG_LIBNL_TINY
     DRV_LIBS += -lnl-tiny
     DRV_CFLAGS += $(shell $(PKG_CONFIG) --cflags libnl-tiny)
+    DRV_CFLAGS += -D_GNU_SOURCE
   else
     ifndef CONFIG_OSX
       DRV_LIBS += -lnl