Add BuildRequires gcc, make, elfutils-libelf-devel

This adds a BuildRequires for gcc, make, and elfutils-libelf-devel
into our spec files. gcc has been a packaging requirement for
awhile now:

https://fedoraproject.org/wiki/Packaging:C_and_C%2B%2B

These additional BuildRequires allow us to mock build in
Fedora 29.

Reviewed-by: Neal Gompa <ngompa@datto.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes #8095
Closes #8102