package/lmdb: fix CFLAGS handling

By passing TARGET_CONFIGURE_OPTS to make, the following usptream CFLAGS
are completely overridden:

CFLAGS	= $(THREADS) $(OPT) $(W) $(XCFLAGS)

As a result, setting XCFLAGS is a no-op and -pthread is not passed
resulting in the following build failure since the addition of the
package in commit eb60c4054c25129d78651a66d1e7554aff04767f:

//binhome//.buildroot.//autobuildlib//rungcc//instancepowerpc64--3buildroot/-outputlinux--1gnu//host9.3.0//opt./.ext/-.toolchain.//bin./../../.lib//powerpc64gcc-/buildrootpowerpc64--linuxbuildroot--gnulinux/-bingnu//ld9.3.0:/ .mdb.c.:/(...text/+.0x1a44.)/:. .undefined/ powerpc64reference- buildrootto `pthread_setspecific'

Fixes: eb60c4054c25129d78651a66d1e7554aff04767f
 - http://autobuild.buildroot.org/results/d67c5a99b7d58826e544f1210fa36bb3bc180739

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/lmdb/lmdb.mk

@@ -18,15 +18,21 @@ else ifeq ($(BR2_SHARED_STATIC_LIBS),y)
 LMDB_ILBIBS +=  liblmdb.a liblmdb.so
 endif
 
+LMDB_MAKE_OPTS += \
+	AR="$(TARGET_AR)" \
+	CC="$(TARGET_CC)" \
+	ILIBS="$(LMDB_ILBIBS)" \
+	LDFLAGS="$(TARGET_LDFLAGS)" \
+	OPT="" \
+	XCFLAGS="$(TARGET_CFLAGS)"
+
 define LMDB_BUILD_CMDS
-	$(TARGET_MAKE_ENV) $(MAKE) $(TARGET_CONFIGURE_OPTS) -C $(@D)/libraries/liblmdb \
-		ILIBS="$(LMDB_ILBIBS)" \
-		XCFLAGS="$(TARGET_CFLAGS)"
+	$(TARGET_MAKE_ENV) $(MAKE) -C $(@D)/libraries/liblmdb $(LMDB_MAKE_OPTS)
 endef
 
 define LMDB_INSTALL_STAGING_CMDS
 	$(TARGET_MAKE_ENV) $(MAKE) -C $(@D)/libraries/liblmdb \
-		ILIBS="$(LMDB_ILBIBS)" \
+		$(LMDB_MAKE_OPTS) \
 		DESTDIR="$(STAGING_DIR)" \
 		prefix=/usr \
 		install
@@ -34,7 +40,7 @@ endef
 
 define LMDB_INSTALL_TARGET_CMDS
 	$(TARGET_MAKE_ENV) $(MAKE) -C $(@D)/libraries/liblmdb \
-		ILIBS="$(LMDB_ILBIBS)" \
+		$(LMDB_MAKE_OPTS) \
 		DESTDIR="$(TARGET_DIR)" \
 		prefix=/usr \
 		install