Remove Windows g++ warnings (#1885)

* remove warnings

* only use with g++

Author: rok-cesnovar

make/compiler_flags

@@ -162,6 +162,10 @@ endif
 ## makes reentrant version lgamma_r available from cmath
 CXXFLAGS_OS += -D_REENTRANT
 
+ifeq (gcc,$(CXX_TYPE))
+CXXFLAGS_WARNINGS += -Wno-int-in-bool-context -Wno-attributes
+endif
+
 ################################################################################
 # Setup OpenCL
 #