update linux build instructions

10 jobs for master in 1 minute and 19 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
canceled #11246
i386 jessie debian
debian_jessie_i386_deb

canceled #11247
x86_64 jessie debian
debian_jessie_x86_64_deb

00:01:19

canceled #11248
x86_64 stretch debian
debian_stretch_x86_64_deb

canceled #11252
dmg v10.11 osx
osx_10.11_x86_64_dmg

canceled #11253
dmg v10.8 osx
osx_10.8_x86_64_dmg

canceled #11255
stretch arm raspbian
raspbian_stretch_armv7l_deb

00:01:17

canceled #11249
i386 v14.04 ubuntu
ubuntu_14.04_i386_deb

canceled #11250
x86_64 v14.04 ubuntu
ubuntu_14.04_x86_64_deb

canceled #11251
x86_64 v16.04 ubuntu
ubuntu_16.04_x86_64_deb

canceled #11254
i386 windows
windows_i386_innosetup