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#11505