do not recursively chmod /etc/apt/keyrings

This step in the installation script was added to take non-standard umasks
into account (which is sometimes the case on some cloud providers).

The existing command was changing modes a bit too eagerly, as it recursively
set the "execute" bit, which would not only affect the /etc/apt/keyrings
directory, but also any file inside it (including files we don't own);

    mkdir -m 0700 keyrings
    touch keyrings/one.sh
    touch keyrings/docker.gpg

    ls -al keyrings/
    total 8
    drwx------  4 root root 128 May  7 11:43 .
    drwx------ 17 root root 544 May  7 11:43 ..
    -rw-r--r--  1 root root   0 May  7 11:43 docker.gpg
    -rw-r--r--  1 root root   0 May  7 11:43 one.sh

    chmod -R a+rx keyrings

    ls -al keyrings/
    total 0
    drwxr-xr-x  4 root root 128 May  7 11:43 .
    drwx------ 17 root root 544 May  7 11:43 ..
    -rwxr-xr-x  1 root root   0 May  7 11:43 docker.gpg
    -rwxr-xr-x  1 root root   0 May  7 11:43 one.sh

This patch changes the script to use `install`, which creates the directory
if it doesn't exist, and sets the permissions on the directory itself, without
recursing to files inside it:

    mkdir -m 0700 keyrings2
    touch keyrings2/one.sh
    touch keyrings2/docker.gpg

    ls -al keyrings2/
    total 8
    drwx------ 2 root root 4096 May  7 11:44 .
    drwxr-xr-x 1 root root 4096 May  7 11:44 ..
    -rw-r--r-- 1 root root    0 May  7 11:44 docker.gpg
    -rw-r--r-- 1 root root    0 May  7 11:44 one.sh

    install -m 0755 -d keyrings2/
    total 8
    drwxr-xr-x 2 root root 4096 May  7 11:44 .
    drwxr-xr-x 1 root root 4096 May  7 11:44 ..
    -rw-r--r-- 1 root root    0 May  7 11:44 docker.gpg
    -rw-r--r-- 1 root root    0 May  7 11:44 one.sh

Changing permissions of the `docker.gpg` file itself is already handled
separately through `chmod a+r /etc/apt/keyrings/docker.gpg`.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

install.sh

@@ -415,7 +415,7 @@ do_install() {
 				fi
 				$sh_c 'apt-get update -qq >/dev/null'
 				$sh_c "DEBIAN_FRONTEND=noninteractive apt-get install -y -qq $pre_reqs >/dev/null"
-				$sh_c 'mkdir -p /etc/apt/keyrings && chmod -R 0755 /etc/apt/keyrings'
+				$sh_c 'install -m 0755 -d /etc/apt/keyrings'
 				$sh_c "curl -fsSL \"$DOWNLOAD_URL/linux/$lsb_dist/gpg\" | gpg --dearmor --yes -o /etc/apt/keyrings/docker.gpg"
 				$sh_c "chmod a+r /etc/apt/keyrings/docker.gpg"
 				$sh_c "echo \"$apt_repo\" > /etc/apt/sources.list.d/docker.list"