Make will honor environment variables like CFLAGS that are used when building and linking.
 
cat << EOF
Help for HDF5 Makefiles
For help with the make utility itself, try 'man make'.
HDF5 makefiles are used to build, test, and install HDF5.  The exact
behavior and output will depend on your system's version of make, compiler,
etc.
Usage: make [make options] [TARGET]
Targets:
make help:      print this help message
make, make all:         (default if no target is specified)
                        builds all libraries, tools, and tests
make lib:               builds libraries only
make progs:             builds libraries and programs
make tests:             builds libraries, programs, and tests.
                        Essentially the same as 'make all'.
make check, make tests,
make _test, make test:  Run HDF5's test suite.
                        Make will exit with a failure if any tests fail.