Update Makefile to create faster binaries.

Update Makefile to create faster binaries:
  - cbust_static:
      Compile a static binary with a recent version of gcc and glibc
      to run on an old distribution as CentOS7. Resulting binary can
      be twice as fast.
  - cbust_amd_libm_aocc:
      Compile a static binary with AMD math library (compiled with AOCC)
      for a slightly faster binary than cbust, or cbust_static.
  - cbust_amd_libm_gcc:
      Compile a static binary with AMD math library (compiled with GCC)
      for a slightly faster binary than cbust, or cbust_static.

Makefile

@@ -3,18 +3,43 @@ GIT_COMMIT_INFO			= $(shell git log -1 --format='%ci  commit: %h')
 CXX				= g++
 ICPC				= icpc
 
-CXXFLAGS			= -Wall -std=c++0x -O3 -march=native -D NDEBUG
+CXXFLAGS			= -Wall -std=c++0x -O3 -march=x86-64 -D NDEBUG
 CXXFLAGS_INTEL			= -Wall -std=c++0x -O3 -march=native -D NDEBUG -static
 CXXFLAGS_GIT_COMMIT_INFO	= -D GIT_COMMIT_INFO="\"$(GIT_COMMIT_INFO)\""
 
+# Optionally compile with AMD Math Library (LibM) for a slightly faster binary:
+#   https://developer.amd.com/amd-aocl/amd-math-library-libm/
+#
+#     mkdir ../aocl-libm
+#     cd ../aocl-libm
+#
+#     AMD_LIB_VERSION=3.1.0
+#
+#     tar xzf aocl-libm-linux-aocc-${AMD_LIB_VERSION}.tar.gz
+#     mv amd-libm amd-libm-aocc
+#
+#     tar xzf aocl-libm-linux-gcc-${AMD_LIB_VERSION}.tar.gz
+#     mv amd-libm amd-libm-gcc
+AMD_LIBM_AOCC			= ../aocl-libm/amd-libm-aocc
+AMD_LIBM_GCC			= ../aocl-libm/amd-libm-gcc
+
 
 all:	cbust
 
 cbust:	*.cpp *.hpp
 	$(CXX) $(CXXFLAGS) $(CXXFLAGS_GIT_COMMIT_INFO) -o cbust *.cpp
 
+cbust_static:	*.cpp *.hpp
+	$(CXX) $(CXXFLAGS) $(CXXFLAGS_GIT_COMMIT_INFO) -o cbust_static *.cpp -static
+
+cbust_amd_libm_aocc:	*.cpp *.hpp
+	$(CXX) $(CXXFLAGS) $(CXXFLAGS_GIT_COMMIT_INFO) -I $(AMD_LIBM_AOCC)/include -o cbust_amd_libm_aocc *.cpp -L $(AMD_LIBM_AOCC)/lib -static -lalm -lm
+
+cbust_amd_libm_gcc:	*.cpp *.hpp
+	$(CXX) $(CXXFLAGS) $(CXXFLAGS_GIT_COMMIT_INFO) -I $(AMD_LIBM_GCC)/include -o cbust_amd_libm_gcc *.cpp -L $(AMD_LIBM_GCC)/lib -static -lalm -lm
+
 cbust_intel:	*.cpp *.hpp
 	$(ICPC) $(CXXFLAGS_INTEL) $(CXXFLAGS_GIT_COMMIT_INFO) -o cbust_intel *.cpp
 
 clean:
-	rm -f cbust cbust_intel
+	rm -f cbust cbust_static cbust_amd_libm_aocc cbust_amd_libm_gcc cbust_intel