Include -lstdc++ under Libs.private in the pkg-config file

This allows linking statically to the library, by passing --static
to pkg-config.

Makefile

@@ -28,6 +28,7 @@ MODULE_NAME=gmpopenh264
 GMP_API_BRANCH=Firefox36
 CCASFLAGS=$(CFLAGS)
 VERSION=1.3
+STATIC_LDFLAGS=-lstdc++
 
 ifeq (,$(wildcard $(SRC_PATH)gmp-api))
 HAVE_GMP_API=No
@@ -220,7 +221,7 @@ $(LIBPREFIX)$(MODULE_NAME).$(SHAREDLIBSUFFIX): $(LIBPREFIX)$(MODULE_NAME).$(SHAR
 endif
 
 $(PROJECT_NAME).pc: $(PROJECT_NAME).pc.in
-	@sed -e 's;@prefix@;$(PREFIX);' -e 's;@VERSION@;$(VERSION);' < $(PROJECT_NAME).pc.in > $@
+	@sed -e 's;@prefix@;$(PREFIX);' -e 's;@VERSION@;$(VERSION);' -e 's;@LIBS_PRIVATE@;$(STATIC_LDFLAGS);' < $(PROJECT_NAME).pc.in > $@
 
 install-headers:
 	mkdir -p $(PREFIX)/include/wels

build/msvc-common.mk

@@ -41,3 +41,4 @@ SHAREDLIBSUFFIXVER=$(SHAREDLIBSUFFIX)
 SHARED=-LD
 EXTRA_LIBRARY=$(PROJECT_NAME)_dll.lib
 SHLDFLAGS=-link -def:openh264.def -implib:$(EXTRA_LIBRARY)
+STATIC_LDFLAGS=

openh264.pc.in

@@ -6,4 +6,5 @@ Name: OpenH264
 Description: OpenH264 is a codec library which supports H.264 encoding and decoding. It is suitable for use in real time applications such as WebRTC.
 Version: @VERSION@
 Libs: -L${libdir} -lopenh264
+Libs.private: @LIBS_PRIVATE@
 Cflags: -I${includedir}