Build: Enable OpenMP support in .pro file

Author: jolavillette

src/libretroshare.pro

@@ -167,6 +167,8 @@ linux-* {
     CONFIG += link_pkgconfig
 
 	QMAKE_CXXFLAGS *= -D_FILE_OFFSET_BITS=64
+	QMAKE_CXXFLAGS += -fopenmp
+	LIBS += -fopenmp
 	QMAKE_CC = $${QMAKE_CXX}
 
     no_sqlcipher {
@@ -242,6 +244,8 @@ win32-x-g++ {
 ################################# Windows ##########################################
 
 win32-g++|win32-clang-g++ {
+	QMAKE_CXXFLAGS += -fopenmp
+	LIBS += -fopenmp
 	QMAKE_CC = $${QMAKE_CXX}
 	OBJECTS_DIR = temp/obj
 	MOC_DIR = temp/moc