Remove -lc++ link and document -fno-exceptions

-lc++ can cause link error on some systems and is not necessary on gcc 4.6+ so remove the link option and document how to build for gcc 4.4

TEST=CC=gcc-4.4 CXXFLAGS=-fno-exceptions CXX=g++-4.4 make -f linux.mk clean all
BUG=libyuv:616

Review URL: https://codereview.chromium.org/2126703003 .

linux.mk

@@ -74,8 +74,10 @@ psnr: util/psnr.cc
 	$(CXX) $(CXXFLAGS) -Iutil/ -o $@ util/psnr.cc util/psnr_main.cc util/ssim.cc
 
 # A C test utility that uses libyuv conversion from C.
+# gcc 4.4 and older require -fno-exceptions to avoid link error on __gxx_personality_v0
+# CC=gcc-4.4 CXXFLAGS=-fno-exceptions CXX=g++-4.4 make -f linux.mk
 cpuid: util/cpuid.c libyuv.a
-	$(CC) $(CFLAGS) -o $@ util/cpuid.c libyuv.a -lc++
+	$(CC) $(CFLAGS) -o $@ util/cpuid.c libyuv.a
 
 clean:
 	/bin/rm -f source/*.o *.ii *.s libyuv.a convert cpuid psnr