Various tweaks to make builds, including FPGA builds, work on Debian
install_gtest.sh: remove Macos 10.9 specific var setting
tools/cdk/include/hdl/hdl-make.mk: force bash for debian
tools/cdk/include/hdl/xst.mk: ditto
tools/cdk/include/xxx-worker.mk: ditto
tools/cdk/include/util.mk: force make SHELL variable to /bin/bash for debian make
tools/cdk/scripts/showRuntimeHost: recognize debian by seeing /etc/os-release