meson,build: Remove some newlines for meson 0.47.1

meson 0.47.1 is failing if the conditions are on multiple lines:

$ meson -Dnmea-source=false -Dmodem-gps-source=false -Dcdma-source=false -D3g-source=false -Ddemo-agent=false -Dgtk-doc=true build
[...]
src/meson.build:93:3: ERROR:  Unknown statement
3 jobs for fix_meson_build in 28 minutes and 18 seconds (queued for 10 seconds)
Status Job ID Name Coverage
  Test
passed #18530
ubuntu-16.04

00:18:34

passed #18531
ubuntu-17.10

00:21:07

passed #18532
ubuntu-18.04

00:19:53