build: fix regression: support local dev builds also using UID!=1000

- both "ELECBUILD_COMMIT fresh_clone builds" and "local dev builds"
  should work even when the unix user has a different UID than 1000
  on the host machine
  - though I guess running as root does not work but that's prob ok

issue was:
```
$ echo $UID
1111
$ ./contrib/build-linux/appimage/build.sh
🗯 ERROR: Building outside a git clone is not supported.
```

Author: SomberNight

contrib/android/Dockerfile

@@ -196,8 +196,8 @@ RUN apt -y update -qq \
 
 
 # create new user to avoid using root; but with sudo access and no password for convenience.
-# NOTE: UID *MUST* align with buildozer's Dockerfile "user"
-RUN useradd -u 1000 -m -s /usr/bin/bash -d /home/user user
+ARG UID=1000
+RUN useradd -u "$UID" -m -s /usr/bin/bash -d /home/user user
 RUN usermod -aG sudo user
 RUN echo "%sudo ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers
 ENV HOME_DIR=/home/user

contrib/build-linux/appimage/Dockerfile

@@ -74,8 +74,8 @@ RUN apt-get update -q && \
     apt-get clean
 
 # create new user to avoid using root; but with sudo access and no password for convenience.
-# NOTE: UID *MUST* align with buildozer's Dockerfile "user"
-RUN useradd -u 1000 -m -s /usr/bin/bash -d /home/user user
+ARG UID=1000
+RUN useradd -u "$UID" -m -s /usr/bin/bash -d /home/user user
 RUN usermod -aG sudo user
 RUN echo "%sudo ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers
 ENV HOME_DIR=/home/user

contrib/build-linux/sdist/Dockerfile

@@ -17,8 +17,8 @@ RUN apt-get update -q && \
     apt-get clean
 
 # create new user to avoid using root; but with sudo access and no password for convenience.
-# NOTE: UID *MUST* align with buildozer's Dockerfile "user"
-RUN useradd -u 1000 -m -s /usr/bin/bash -d /home/user user
+ARG UID=1000
+RUN useradd -u "$UID" -m -s /usr/bin/bash -d /home/user user
 RUN usermod -aG sudo user
 RUN echo "%sudo ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers
 ENV HOME_DIR=/home/user

contrib/build-wine/Dockerfile

@@ -57,8 +57,8 @@ RUN DEBIAN_CODENAME=$(lsb_release --codename --short) && \
     apt-get clean
 
 # create new user to avoid using root; but with sudo access and no password for convenience.
-# NOTE: UID *MUST* align with buildozer's Dockerfile "user"
-RUN useradd -u 1000 -m -s /usr/bin/bash -d /home/user user
+ARG UID=1000
+RUN useradd -u "$UID" -m -s /usr/bin/bash -d /home/user user
 RUN usermod -aG sudo user
 RUN echo "%sudo ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers
 ENV HOME_DIR=/home/user