In preparation for single-pass shared/static CMake builds.

Ref: curl/curl#11505

Making it clear that the measurement was done with separate shared and
static build passes, and without this patch:

curl/curl@1199308
curl/curl#11505

…elease [ci skip]

Using this new cmake build option:
curl/curl@1199308
curl/curl#11505

Follow-up to 1199308 curl#11505

Reported-by: balikalina on Github
Fixes curl@1199308#r123923098
Closes #xxxxx

Replace (wrong) literal with a variable to specify the curl
namespace.

Follow-up to 1199308 #11505

Reported-by: balikalina on Github
Fixes 1199308#r123923098
Closes #11629

Fixes:
```
[25/26] -- Found CURL: ***/build/parts/curl/install/lib64/cmake/CURL/CURLConfig.cmake (found version "8.3.0-DEV")
[25/26] CMake Error at ***/build/parts/curl/install/lib64/cmake/CURL/CURLConfig.cmake:62 (add_library):
[25/26]   add_library cannot create ALIAS target "CURL::libcurl" because target
[25/26]   "CURL::libcurl_static" is imported but not globally visible.
```

Follow-up to 1199308 curl#11505

Reported-by: balikalina on Github
Suggested-by: balikalina on Github
Ref: curl#11629 (comment)
Closes #xxxxx

Fixes:
```
[25/26] -- Found CURL: ***/build/parts/curl/install/lib64/cmake/CURL/CURLConfig.cmake (found version "8.3.0-DEV")
[25/26] CMake Error at ***/build/parts/curl/install/lib64/cmake/CURL/CURLConfig.cmake:62 (add_library):
[25/26]   add_library cannot create ALIAS target "CURL::libcurl" because target
[25/26]   "CURL::libcurl_static" is imported but not globally visible.
```

Follow-up to 1199308 curl#11505

Reported-by: balikalina on Github
Suggested-by: balikalina on Github
Ref: curl#11629 (comment)
Closes #xxxxx

This patch adds the ability to build a static and shared libcurl library
in a single build session. It also adds an option to select which one to
use when building the curl executable.

New build options:
- `BUILD_STATIC_LIBS`. Default: `OFF`.
  Enabled automatically if `BUILD_SHARED_LIBS` is `OFF`.
- `BUILD_STATIC_CURL`. Default: `OFF`.
  Requires `BUILD_STATIC_LIBS` enabled.
  Enabled automatically if building static libcurl only.
- `STATIC_LIB_SUFFIX`. Default: empty.
- `IMPORT_LIB_SUFFIX`. Default: `_imp` if implib filename would collide
  with static lib name (typically with MSVC) in Windows builds.
  Otherwise empty.

Also:

- Stop setting the `CURL_STATICLIB` macro via `curl_config.h`, and pass
  it directly to the compiler. This also allows to delete a condition
  from `tests/server/CMakeLists.txt`.

- Complete a TODO by following the logic used in autotools (also for
  `LIBCURL_NO_SHARED`), and set `-DCURL_STATICLIB` in `Cflags:` of
  `libcurl.pc` for _static-only_ curl builds.

- Convert an existing CI test to build both shared and static libcurl.

Closes curl#11505

Replace (wrong) literal with a variable to specify the curl
namespace.

Follow-up to 1199308 curl#11505

Reported-by: balikalina on Github
Fixes curl@1199308#r123923098
Closes curl#11629

Switch from `curl-gnumake.sh` to `curl-cmake.sh` with upcoming curl
release v8.5.0.

cmake builds are now _faster_ for Windows builds than raw gnumake
(aka `Makefile.mk`). They also use 'unity' mode, which makes builds
run fast with the side-effect of also creating potentially more
efficient binaries by allowing better compiler optimizations.

This also makes curl-for-win use the same build system for all target
platforms (`Makefile.mk` is not available for *nix platforms).

Initially on 2022-07-04 cmake was 25% slower than gnumake. By
2022-09-26 this reduced to 20%, by 2023-07-29 to 18% and after the
latest round of updates gnumake came out 7% slower than cmake.
This is for Windows, for a triple x64, arm64 and x86 build. In
absolute times this is 27m22s for cmake and 29m11s for gnumake.

(FWIW autotools builds are 52% slower than cmake unity builds now.)

Making cmake builds fast was a multi-year effort with these major steps:

1. add support for cmake builds in curl-for-win.
   420e73c
2. bring it in-line with gnumake and autotools builds and tidy-up
   as much as possible. Scattered to a many commits.
3. delete a whole bunch of unused feature detections.
   curl/curl@4d73854
   curl/curl#9044
   (and a lot more smaller commits)
4. speed up picky warning option initialization by avoiding brute-force
   all options. (first in libssh2, then in curl, then applied also
   ngtcp2, nghttp3, nghttp2)
   curl/curl@9c543de
   curl/curl#10973
5. implement single build run for shared and static libcurl + tool
   (first in libssh2)
   curl/curl@1199308
   curl/curl#11505
   53dcd49
6. implement single build pass for shared and static libcurl
   (for Windows initially)
   curl/curl@2ebc74c
   curl/curl#11546
7. extend above to non-Windows (e.g. macOS)
   curl/curl@fc9bfb1
   curl/curl#11627
   bafa77d (mac)
   1b27304 (linux)
8. implement unity builds: single compiler invocation for libcurl + tool
   curl/curl@3f8fc25
   curl/curl#11095
   curl/curl@f42a279
   curl/curl#11928
   67d7fd3
9. speed up 4x the cmake initialization phase (for Windows)
   curl/curl@2100d9f
   curl/curl#12044
10. speed up cmake initialization even more by pre-filling
   detection results for our well-known mingw-w64 environments.
   74dd967
   5a43c61

+1: speed up autotools initialization by mitigating a brute-force
   feature detection on Windows. This reduced total build times
   by 5 minutes at the time, for the 3 Windows targets in total.
   curl/curl@6adcff6
   curl/curl#9591

Also update build times for cmake-unity and gnumake, based on runs:
cmake-unity: https://ci.appveyor.com/project/curlorg/curl-for-win/builds/48357875
gnumake: https://ci.appveyor.com/project/curlorg/curl-for-win/builds/48358005