python: Fix CPPFLAGS and LDFLAGS for Linuxbrew
python: Fix CPPFLAGS and LDFLAGS for Linuxbrew

Fix configure: error: cannot run C compiled programs.

See Linuxbrew/linuxbrew#420, Linuxbrew/linuxbrew#460,
and Linuxbrew/linuxbrew#875.

sjackman/linuxbrew,saketkc/linuxbrew,Linuxbrew/linuxbrew,saketkc/linuxbrew,Homebrew/linuxbrew,SuperNEMO-DBD/cadfaelbrew,Homebrew/linuxbrew,Angeldude/linuxbrew,Linuxbrew/linuxbrew,reelsense/linuxbrew,Homebrew/linuxbrew,reelsense/linuxbrew,sjackman/linuxbrew,Linuxbrew/linuxbrew,reelsense/linuxbrew,gnubila-france/linuxbrew,sjackman/linuxbrew,Linuxbrew/linuxbrew,gnubila-france/linuxbrew,saketkc/linuxbrew,Angeldude/linuxbrew,gnubila-france/linuxbrew,sjackman/linuxbrew,saketkc/linuxbrew,Angeldude/linuxbrew,Angeldude/linuxbrew,SuperNEMO-DBD/cadfaelbrew,gnubila-france/linuxbrew,SuperNEMO-DBD/cadfaelbrew,reelsense/linuxbrew,Homebrew/linuxbrew,SuperNEMO-DBD/cadfaelbrew