Native MIDI: Try fix MinGW distro compilation bug

win32/Makefile

@@ -6,6 +6,8 @@ TEST_TARGET = sdlpal-tests.exe
 HOST =
 TEST_CCFLAGS =
 
+GCCV6P := $(shell expr `$(HOST)g++ -dumpversion | cut -f1 -d.` \>= 6)
+
 GTEST_DIR = ../3rd/googletest/googletest
 
 CFILES = $(wildcard ../adplug/*.c) $(wildcard ../libmad/*.c) $(wildcard ../liboggvorbis/src/*.c) $(wildcard ../*.c) $(wildcard ../native_midi/*.c) $(wildcard ../win32/*.c)
@@ -16,8 +18,12 @@ TEST_CPPFILES = $(wildcard ../tests/*.cpp)
 TEST_OBJFILES = $(TEST_CPPFILES:.cpp=.o)
 
 override CCFLAGS += `sdl2-config --cflags` -g -msse2 -Wall -O2 -fno-strict-aliasing -I. -I../ -I../liboggvorbis/include -I../liboggvorbis/src -DPAL_HAS_PLATFORM_SPECIFIC_UTILS $(TEST_CCFLAGS)
-CXXFLAGS = $(CCFLAGS) -std=c++11
+CXXFLAGS = $(CCFLAGS)
 CFLAGS = $(CCFLAGS) -std=gnu99
+# GCC v6 or higher has already defaults to gnu++14
+ifeq "$(GCCV6P)" "0"
+    CXXFLAGS += -std=c++11
+endif
 LDFLAGS = `sdl2-config --libs` -lm -lwinmm -lole32 -loleaut32 -limm32 -lcomctl32 -luuid -ldxguid -lversion -static -static-libgcc -static-libstdc++
 TEST_CXXFLAGS += -isystem $(GTEST_DIR)/include -I $(GTEST_DIR) -g -Wall -Wextra -pthread
 

win32/Makefile.mingw

@@ -6,6 +6,8 @@ TEST_TARGET = sdlpal-tests.exe
 HOST =
 TEST_CCFLAGS =
 
+GCCV6P := $(shell expr `$(HOST)g++ -dumpversion | cut -f1 -d.` \>= 6)
+
 GTEST_DIR = ../3rd/googletest/googletest
 
 CFILES = $(wildcard ../adplug/*.c) $(wildcard ../libmad/*.c) $(wildcard ../liboggvorbis/src/*.c) $(wildcard ../*.c) $(wildcard ../native_midi/*.c) $(wildcard ../win32/*.c)
@@ -16,8 +18,12 @@ TEST_CPPFILES = $(wildcard ../tests/*.cpp)
 TEST_OBJFILES = $(TEST_CPPFILES:.cpp=.o)
 
 override CCFLAGS += -g -msse2 -Wall -O2 -fno-strict-aliasing -I. -I../ -I../liboggvorbis/include -I../liboggvorbis/src -DPAL_HAS_PLATFORM_SPECIFIC_UTILS $(TEST_CCFLAGS)
-CXXFLAGS = $(CCFLAGS) -std=c++11
+CXXFLAGS = $(CCFLAGS)
 CFLAGS = $(CCFLAGS) -std=gnu99
+# GCC v6 or higher has already defaults to gnu++14
+ifeq "$(GCCV6P)" "0"
+    CXXFLAGS += -std=c++11
+endif
 LDFLAGS = -lmingw32 -lSDL2main -lSDL2 -mwindows -lm -lwinmm -lole32 -loleaut32 -limm32 -lcomctl32 -luuid -ldxguid -lversion -static -static-libgcc -static-libstdc++
 TEST_CXXFLAGS += -isystem $(GTEST_DIR)/include -I $(GTEST_DIR) -g -Wall -Wextra -pthread