to give the location of libunwind for gperftools

The way of giving the location of libunwind to the configure script of gperftools:

%setenv CFLAGS="-I /path/to/LIBUNWIND/include -L/path/to/LIBUNWIND/lib"
%setenv CXXFLAGS="-I /path/to/LIBUNWIND/include -L/path/to/LIBUNWIND/lib"
%./configure --prefix=/path/to/install

Interestingly, the configure script does not have the option.

https://github.com/gperftools/gperftools