package/zstd: rework build and install

Create libzstd.pc in the build step instead of triggering a
lazy build during installation when it is missing.

Move PREFIX=/usr to ZSTD_OPTS. It is needed for building libzstd.pc
during the build step; for consistency, make sure it's available in all
steps.

Attach '-release' to the targets, since the default is to
build lib-release and zstd-release. Its only effect is to clear
DEBUGFLAGS (which are just warning flags).

Signed-off-by: Norbert Lange <nolange79@gmail.com>
[Arnout: add check-package disable]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/zstd/zstd.mk

@@ -12,6 +12,7 @@ ZSTD_LICENSE_FILES = LICENSE COPYING
 ZSTD_CPE_ID_VENDOR = facebook
 ZSTD_CPE_ID_PRODUCT = zstandard
 
+ZSTD_OPTS += PREFIX=/usr
 ZSTD_OPTS += ZSTD_LEGACY_SUPPORT=0
 ifeq ($(BR2_PACKAGE_ZLIB),y)
 ZSTD_DEPENDENCIES += zlib
@@ -60,12 +61,14 @@ else
 ZSTD_OPTS += HAVE_THREAD=0
 ZSTD_BUILD_LIBS := $(addsuffix -nomt,$(ZSTD_BUILD_LIBS))
 endif
+# check-package disable OverriddenVariable - override intended
+ZSTD_BUILD_LIBS := $(addsuffix -release,$(ZSTD_BUILD_LIBS))
 
 define ZSTD_BUILD_CMDS
 	$(TARGET_MAKE_ENV) $(TARGET_CONFIGURE_OPTS) $(MAKE) $(ZSTD_OPTS) \
-		-C $(@D)/lib $(ZSTD_BUILD_LIBS)
+		-C $(@D)/lib $(ZSTD_BUILD_LIBS) libzstd.pc
 	$(TARGET_MAKE_ENV) $(TARGET_CONFIGURE_OPTS) $(MAKE) $(ZSTD_OPTS) \
-		-C $(@D) zstd
+		-C $(@D) zstd-release
 endef
 
 define ZSTD_INSTALL_STAGING_CMDS
@@ -76,9 +79,9 @@ endef
 
 define ZSTD_INSTALL_TARGET_CMDS
 	$(TARGET_MAKE_ENV) $(TARGET_CONFIGURE_OPTS) $(MAKE) $(ZSTD_OPTS) \
-		DESTDIR=$(TARGET_DIR) PREFIX=/usr -C $(@D)/programs install
+		DESTDIR=$(TARGET_DIR) -C $(@D)/programs install
 	$(TARGET_MAKE_ENV) $(TARGET_CONFIGURE_OPTS) $(MAKE) $(ZSTD_OPTS) \
-		DESTDIR=$(TARGET_DIR) PREFIX=/usr -C $(@D)/lib $(ZSTD_INSTALL_LIBS)
+		DESTDIR=$(TARGET_DIR) -C $(@D)/lib $(ZSTD_INSTALL_LIBS)
 endef
 
 HOST_ZSTD_OPTS += PREFIX=$(HOST_DIR)