CMake pkg-config windows: fix static library options

pkg-config uses the .private suffix for static linking to c-ares,
set the libraries and cflags necessary for this.

Authored-By: Christoph Reiter (@lazka)
Approved-By: Brad House (@bradh352)

CMakeLists.txt

@@ -772,12 +772,11 @@ IF (CARES_INSTALL)
 	INSTALL (EXPORT ${PROJECT_NAME}-targets COMPONENT Devel DESTINATION ${CMAKECONFIG_INSTALL_DIR} NAMESPACE ${PROJECT_NAME}::)
 	INSTALL (FILES "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}-config.cmake" "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}-config-version.cmake" COMPONENT Devel DESTINATION ${CMAKECONFIG_INSTALL_DIR})
 
-	# pkgconfig support
-	IF (NOT CARES_SHARED)
-		FOREACH (LIB ${CARES_DEPENDENT_LIBS})
-			SET (CARES_PRIVATE_LIBS "${CARES_PRIVATE_LIBS} -l${LIB}")
-		ENDFOREACH ()
-	ENDIF ()
+	# pkgconfig support for static builds
+	FOREACH (LIB ${CARES_DEPENDENT_LIBS})
+		SET (CARES_PRIVATE_LIBS "${CARES_PRIVATE_LIBS} -l${LIB}")
+	ENDFOREACH ()
+
 	CONFIGURE_FILE("libcares.pc.cmake" "libcares.pc" @ONLY)
 	INSTALL (FILES "${CMAKE_CURRENT_BINARY_DIR}/libcares.pc" COMPONENT Devel DESTINATION "${CMAKE_INSTALL_LIBDIR}/pkgconfig")
 ENDIF ()

libcares.pc.cmake

@@ -7,9 +7,9 @@
 # Copyright (C) The c-ares project and its contributors
 # SPDX-License-Identifier: MIT
 prefix=@CMAKE_INSTALL_PREFIX@
-exec_prefix=@CMAKE_INSTALL_FULL_BINDIR@
-libdir=@CMAKE_INSTALL_FULL_LIBDIR@
-includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+exec_prefix=${prefix}/@CMAKE_INSTALL_BINDIR@
+libdir=${prefix}/@CMAKE_INSTALL_LIBDIR@
+includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
 
 Name: c-ares
 URL: https://c-ares.org/
@@ -18,5 +18,6 @@ Version: @CARES_VERSION@
 Requires: 
 Requires.private: 
 Cflags: -I${includedir}
+Cflags.private: -DCARES_STATICLIB
 Libs: -L${libdir} -lcares
 Libs.private: @CARES_PRIVATE_LIBS@