docs: improve dev setup command lines

use `meson ... -C build` as it seems more common than getting into the
build dir before running the `meson` command-lines.

Author: MightyCreak

docs/developers/developers-setup.md

@@ -80,15 +80,15 @@ flatpak-builder --user --install build-flatpak io.github.mightycreak.Diffuse.yml
 To run Diffuse through Flatpak:
 
 ```sh
-flatpak run io.github.mightycreak.Diffuse
+flatpak run --user io.github.mightycreak.Diffuse
 ```
 
 #### Uninstall
 
 To uninstall Diffuse:
 
 ```sh
-flatpak remove io.github.mightycreak.Diffuse
+flatpak remove --user io.github.mightycreak.Diffuse
 ```
 
 ### Setup on Linux using Meson
@@ -101,17 +101,16 @@ To build and test Diffuse:
 
 ```sh
 meson setup build
-cd build
-meson compile
-meson test
+meson compile -C build
+meson test -C build
 ```
 
 #### Install on system and run
 
 To install Diffuse on your system (e.g. `/usr/local/`):
 
 ```sh
-meson install  # requires admin privileges
+meson install -C build  # requires admin privileges
 ```
 
 To run Diffuse:
@@ -128,7 +127,7 @@ Meson allows to change the default installation directories, see
 To install Diffuse in a custom directory (e.g. `~/bin/diffuse`):
 
 ```sh
-meson install --destdir ~/bin/diffuse
+meson install -C build --destdir ~/bin/diffuse
 ```
 
 To run Diffuse:
@@ -159,9 +158,8 @@ To build and test Diffuse:
 
 ```sh
 meson setup build
-cd build
-meson compile
-meson test
+meson compile -C build
+meson test -C build
 ```
 
 #### Install on system and run
@@ -170,7 +168,7 @@ To install Diffuse on your system (e.g. `/Applications/` and `/opt/homebrew/`
 or `/usr/local/`):
 
 ```sh
-meson install  # requires admin privileges
+meson install -C build  # requires admin privileges
 ```
 
 To run Diffuse: