package/libselinux: fix host build

The following build failure is raised since commit
1745fcde740057951dcc5429f3bfabd103b764a1 because
$(HOST_PKG_PYTHON_DISTUTILS_ENV) contains $(HOST_CONFIGURE_OPTS) and so
will override LDFLAGS passed by libselinux.mk:

/usr/bin/gcc -O2 -I/nvmedata/autobuild/instance-11/output-1/host/include -I../include -D_GNU_SOURCE  -DNO_ANDROID_BACKEND  -L/nvmedata/autobuild/instance-11/output-1/host/lib -Wl,-rpath,/nvmedata/autobuild/instance-11/output-1/host/lib -shared -o libselinux.so.1 avc.lo avc_internal.lo avc_sidtab.lo booleans.lo callbacks.lo canonicalize_context.lo checkAccess.lo check_context.lo checkreqprot.lo compute_av.lo compute_create.lo compute_member.lo compute_relabel.lo compute_user.lo context.lo deny_unknown.lo disable.lo enabled.lo fgetfilecon.lo freecon.lo freeconary.lo fsetfilecon.lo get_context_list.lo get_default_type.lo get_initial_context.lo getenforce.lo getfilecon.lo getpeercon.lo init.lo is_customizable_type.lo label.lo label_db.lo label_file.lo label_media.lo label_support.lo label_x.lo lgetfilecon.lo load_policy.lo lsetfilecon.lo mapping.lo matchmediacon.lo matchpathcon.lo policyvers.lo procattr.lo query_user_context.lo regex.lo reject_unknown.lo selinux_check_securetty_context.l
 o selinux_config.lo selinux_restorecon.lo sestatus.lo setenforce.lo setexecfilecon.lo setfilecon.lo setrans_client.lo seusers.lo sha1.lo stringrep.lo validatetrans.lo   -ldl -Wl,-soname,libselinux.so.1,--version-script=libselinux.map,-z,defs,-z,relro
/usr/bin/ld: regex.lo: in function `regex_writef':
regex.c:(.text+0x7c): undefined reference to `pcre_fullinfo'

To fix this build failure, instead of moving LDFLAGS after
$(HOST_PKG_PYTHON_DISTUTILS_ENV), drop LDFLAGS and add host-pkgconf
dependency to retrieve pcre dependencies as pkg-config is supported
since version 3.2 and
https://github.com/SELinuxProject/selinux/commit/74093beab0c605641ec413be81e31e6b2f55d8d4

Dropping LDFLAGS will also drop -lpthread which doesn't seem to raise
any build failures with test-pkg:

                    bootlin-armv5-uclibc [1/6]: OK
                     bootlin-armv7-glibc [2/6]: OK
                   bootlin-armv7m-uclibc [3/6]: SKIPPED
                     bootlin-x86-64-musl [4/6]: OK
                      br-arm-full-static [5/6]: SKIPPED
                            sourcery-arm [6/6]: SKIPPED

Apply the same update to the target variant for consistency.

Fixes:
 - http://autobuild.buildroot.org/results/d16995f0decef9c9bf58cab4fa30f7daab6918fb

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/libselinux/libselinux.mk

@@ -10,7 +10,8 @@ LIBSELINUX_LICENSE = Public Domain
 LIBSELINUX_LICENSE_FILES = LICENSE
 LIBSELINUX_CPE_ID_VENDOR = selinuxproject
 
-LIBSELINUX_DEPENDENCIES = $(BR2_COREUTILS_HOST_DEPENDENCY) libsepol pcre
+LIBSELINUX_DEPENDENCIES = \
+	$(BR2_COREUTILS_HOST_DEPENDENCY) host-pkgconf libsepol pcre
 
 LIBSELINUX_INSTALL_STAGING = YES
 
@@ -52,8 +53,7 @@ endif # python3
 # when the python binding is enabled.
 LIBSELINUX_MAKE_OPTS += \
 	CFLAGS="$(filter-out -D_FILE_OFFSET_BITS=64,$(TARGET_CFLAGS))" \
-	CPPFLAGS="$(filter-out -D_FILE_OFFSET_BITS=64,$(TARGET_CPPFLAGS))" \
-	LDFLAGS="$(TARGET_LDFLAGS) -lpcre -lpthread"
+	CPPFLAGS="$(filter-out -D_FILE_OFFSET_BITS=64,$(TARGET_CPPFLAGS))"
 
 define LIBSELINUX_BUILD_CMDS
 	$(TARGET_MAKE_ENV) $(MAKE) -C $(@D) \
@@ -76,13 +76,12 @@ define LIBSELINUX_INSTALL_TARGET_CMDS
 endef
 
 HOST_LIBSELINUX_DEPENDENCIES = \
-	host-libsepol host-pcre host-swig host-python3
+	host-pkgconf host-libsepol host-pcre host-swig host-python3
 
 HOST_LIBSELINUX_MAKE_OPTS = \
 	$(HOST_CONFIGURE_OPTS) \
 	PREFIX=$(HOST_DIR) \
 	SHLIBDIR=$(HOST_DIR)/lib \
-	LDFLAGS="$(HOST_LDFLAGS) -lpcre -lpthread" \
 	$(HOST_PKG_PYTHON_DISTUTILS_ENV) \
 	PYTHON=python$(PYTHON3_VERSION_MAJOR)