make install can fail with parallel make

[Shaun Jackman]

`make install` can fail with parallel make. `make -j1` works around the issue.
See https://github.com/Homebrew/homebrew-dupes/issues/622
and https://github.com/Homebrew/homebrew-dupes/pull/630

```
installing ../lib/libncursesw.a as
/home/nh79w/.linuxbrew/Cellar/ncurses/6.0_1/lib/libncursesw.a
/home/nh79w/.linuxbrew/bin/ginstall -c -m 644 ../lib/libncursesw.a
/home/nh79w/.linuxbrew/Cellar/ncurses/6.0_1/lib/libncursesw.a
ranlib /home/nh79w/.linuxbrew/Cellar/ncurses/6.0_1/lib/libncursesw.a
installing ../lib/libncursesw_g.a as
/home/nh79w/.linuxbrew/Cellar/ncurses/6.0_1/lib/libncursesw_g.a
/home/nh79w/.linuxbrew/bin/ginstall -c -m 644 ../lib/libncursesw_g.a
/home/nh79w/.linuxbrew/Cellar/ncurses/6.0_1/lib/libncursesw_g.a
/home/nh79w/.linuxbrew/bin/ginstall: cannot stat
'../lib/libncursesw_g.a': No such file or directory
make[1]: *** [Makefile:2840: install] Error 1
make[1]: Leaving directory
'/tmp/ncurses-20160613-61631-qne5hl/ncurses-6.0/ncurses'
make: *** [Makefile:115: install] Error 2
```

Cheers,
Shaun

--
Shaun Jackman
http://sjackman.ca