build: raise cmake_minimum_required to 3.18

libcurl requires CMake 3.18 [1], and nghttp2 asks for 3.14 since
1.70.0 [2]. We build both as ExternalProjects and a fresh CMake is a
prerequisite to update these dependencies.

Modern Linux distros offer 3.18 or newer, but some EOL ones don't:
CentOS 7, Ubuntu 20.04 for example. PackPack backports repositories
offer CMake 3.18 for some of them, see [3].

3.5 -> 3.18 sets 43 policies to NEW (CMP0066..CMP0108). Only CMP0082
changes the generated files: install rules from `add_subdirectory()`
now run where the call is, not after all rules of the current scope.
It only reorders src/lib and src/box, which install nothing. CMP0068
is the only behaviour change we could meet, on macOS only:
`CMAKE_SKIP_RPATH` stops suppressing `install_name` for our dynamic
libraries, which are not installed and used only for testing.

Shifting the minimum CMake version allows to eliminate a few
workarounds created for older versions. I plan to remove them in a
separate series.

[1]: curl/curl#20407
[2]: https://github.com/nghttp2/nghttp2/blob/v1.70.0/CMakeLists.txt
[3]: https://github.com/orgs/packpack/discussions/159

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

Fixes tarantool#13306

NO_CHANGELOG=build
NO_DOC=build
NO_TEST=build

Author: Totktonada

.github/workflows/static_build_cmake_linux.yml

@@ -89,13 +89,12 @@ jobs:
         with:
           submodule: ${{ inputs.submodule }}
           revision: ${{ inputs.revision }}
-      # Install CMake using PyPI, because option
-      # `--repeat until-pass:3` required by CTest was added since
-      # CMake 3.17.
+      # Install CMake using PyPI: the container's CMake is older
+      # than the minimum required by the project.
       - name: install cmake
         run: |
           apt -y remove cmake
-          pip3 install cmake==3.17.3
+          pip3 install cmake==3.18.4.post1
       - name: test
         run: make -f .test.mk test-static-cmake
       - name: Send VK Teams message on failure

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 3.18)
 
 project(tarantool C CXX ASM)
 

static-build/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 3.18)
 
 # Detect system compilers for further dependencies configuring to be
 # built with these compilers. This is used to build tarantool and