python3: Add lib to LDFLAGS for Linuxbrew
python3: Add lib to LDFLAGS for Linuxbrew

Added -L#{HOMEBREW_PREFIX}/lib to LDFLAGS passed to configure call so
that Python's setup.py could find "necessary bits" to build extensions.

Closes Linuxbrew/linuxbrew#886.

Signed-off-by: Shaun Jackman <b580dab3251a9622aba3803114310c23fdb42900@gmail.com>

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