Fix Up #2659; Build libzstd.pc Whenever Building the Lib on Unix

lib/Makefile

@@ -175,7 +175,7 @@ endif  # if windows
 libzstd : $(LIBZSTD)
 
 .PHONY: lib
-lib : libzstd.a libzstd libzstd.pc
+lib : libzstd.a libzstd
 
 
 # note : do not define lib-mt or lib-release as .PHONY
@@ -246,24 +246,12 @@ clean:
 	$(RM) -r obj/*
 	@echo Cleaning library completed
 
-libzstd.pc:
-libzstd.pc: libzstd.pc.in
-	@echo creating pkgconfig
-	@sed $(SED_ERE_OPT) \
-		-e 's|@PREFIX@|$(PREFIX)|' \
-		-e 's|@EXEC_PREFIX@|$(PCEXEC_PREFIX)|' \
-		-e 's|@INCLUDEDIR@|$(PCINCPREFIX)$(PCINCDIR)|' \
-		-e 's|@LIBDIR@|$(PCLIBPREFIX)$(PCLIBDIR)|' \
-		-e 's|@VERSION@|$(VERSION)|' \
-		-e 's|@LIBS_PRIVATE@|$(LDFLAGS_DYNLIB)|' \
-		$< >$@
-
 #-----------------------------------------------------------------------------
 # make install is validated only for below listed environments
 #-----------------------------------------------------------------------------
 ifneq (,$(filter $(UNAME),Linux Darwin GNU/kFreeBSD GNU OpenBSD FreeBSD NetBSD DragonFly SunOS Haiku AIX))
 
-all: libzstd.pc
+lib: libzstd.pc
 
 HAS_EXPLICIT_EXEC_PREFIX := $(if $(or $(EXEC_PREFIX),$(exec_prefix)),1,)
 
@@ -308,6 +296,17 @@ INSTALL_PROGRAM ?= $(INSTALL)
 INSTALL_DATA    ?= $(INSTALL) -m 644
 
 
+libzstd.pc: libzstd.pc.in
+	@echo creating pkgconfig
+	@sed $(SED_ERE_OPT) \
+	        -e 's|@PREFIX@|$(PREFIX)|' \
+	        -e 's|@EXEC_PREFIX@|$(PCEXEC_PREFIX)|' \
+	        -e 's|@INCLUDEDIR@|$(PCINCPREFIX)$(PCINCDIR)|' \
+	        -e 's|@LIBDIR@|$(PCLIBPREFIX)$(PCLIBDIR)|' \
+	        -e 's|@VERSION@|$(VERSION)|' \
+	        -e 's|@LIBS_PRIVATE@|$(LDFLAGS_DYNLIB)|' \
+	        $< >$@
+
 .PHONY: install
 install: install-pc install-static install-shared install-includes
 	@echo zstd static and shared library installed