ci: use uname -m to download CMake in install-deps-debian

The action determines the host's architecture using `uname` to download
the proper CMake distribution.

`uname -i` is not portable [1] and gives `unknown` on Ubuntu 26.04.
`uname -m` gives `x86_64` and `aarch64` everywhere, matching the archive
names.

Ubuntu 26.04 runners offered by GitHub have CMake 4.4.3 preinstalled, so
we don't hit this problem: the version check skips the CMake 3.26.0
installation.

Also, while we're here, let the `curl`+`tar` sequence fail the step on a
failed download: add the `-f` flag to `curl` and split the `&&` command
sequence (`bash -e` ignores a failure of any command but the last in a
`&&` sequence [2]).

[1]: https://www.gnu.org/software/coreutils/manual/html_node/uname-invocation.html
[2]: https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html

Drafted by an LLM, conducted and corrected by the commit author.

NO_DOC=ci
NO_TEST=ci
NO_CHANGELOG=ci

Author: Totktonada

.github/actions/install-deps-debian/action.yml

@@ -24,18 +24,20 @@ runs:
           util-linux
         # Install cmake 3.26.0 if cmake was missing or the cmake version was
         # less than 3.26.0.
+        CMAKE_VERSION=3.26.0
         version_gt() {
           [ "$1" != "$2" ] && [ "$2" = "$(printf '%s\n' "$1" "$2" | sort -V | head -n1)" ]
         }
         CURRENT_VERSION="0.0.0"
         if command -v cmake >/dev/null 2>&1; then
           CURRENT_VERSION=$(cmake --version | head -n 1 | awk '{print $3}')
         fi
-        if version_gt "3.26.0" "$CURRENT_VERSION"; then
+        if version_gt "$CMAKE_VERSION" "$CURRENT_VERSION"; then
           ${SUDO} apt-get purge --auto-remove cmake -y
-          curl -O -L https://github.com/Kitware/CMake/releases/download/v3.26.0/cmake-3.26.0-linux-$(uname -i).tar.gz \
-          && ${SUDO} tar -xvf cmake-3.26.0-linux-$(uname -i).tar.gz -C /usr/local --strip-components=1 \
-          && rm cmake-3.26.0-linux-$(uname -i).tar.gz
+          ARCH=$(uname -m)
+          curl -f -O -L https://github.com/Kitware/CMake/releases/download/v${CMAKE_VERSION}/cmake-${CMAKE_VERSION}-linux-${ARCH}.tar.gz
+          ${SUDO} tar -xvf cmake-${CMAKE_VERSION}-linux-${ARCH}.tar.gz -C /usr/local --strip-components=1
+          rm cmake-${CMAKE_VERSION}-linux-${ARCH}.tar.gz
         fi
         # (Re)install luacheck only if it is not installed (or if another
         # version is installed).