Compiler upgrade recipes

Native compiler toolchains can be persnickety and mysterious. Changing a working configuration to use a different one can be doubly so. Here are some helpful tips when interpreting error messages from builds of native crates:

• CFLAGS is different from CXXFLAGS is different from CPPFLAGS
• when modifying CPPFLAGS, ensure that any include paths present in CFLAGS/CXXFLAGS are also present in CPPFLAGS
• When using a clang compiler, -v will print out the list of include paths and their relative order
• Be careful when using -v in CFLAGS/CXXFLAGS and a version of cc-rs that does not include this change