Bug 31538: Bump CMake version

The old CMake version built libraries like libc++.a and libc++abi.a in a
non-reproducible way. Using the latest CMake version solves that.

We need to use our own GCC for Linux as the shippped one is too old.

projects/cmake/build

 #!/bin/bash
 [% c("var/set_default_env") -%]
 distdir=/var/tmp/dist/[% project %]
-mkdir -p /var/tmp/build
+[% IF c("var/linux") %]
+  [% pc('gcc', 'var/setup', { compiler_tarfile => c('input_files_by_name/gcc'),
+                              hardened_gcc => 0 }) %]
+[% END -%]
+mkdir /var/tmp/build
 tar -C /var/tmp/build -xf [% project %]-[% c('version') %].tar.gz
 cd /var/tmp/build/[% project %]-[% c('version') %]
 ./bootstrap --prefix=$distdir

projects/cmake/config

 # vim: filetype=yaml sw=2
-version: 3.4.3
+version: 3.15.3
 git_url: https://cmake.org/cmake.git
 git_hash: 'v[% c("version") %]'
 tag_gpg_id: 1
@@ -11,3 +11,6 @@ var:
 
 input_files:
   - project: container-image
+  - name: '[% c("var/compiler") %]'
+    project: '[% c("var/compiler") %]'
+    enable: '[% c("var/linux") %]'