improve static-library build

[basiliscos]

When I launch CMake with the following parameters:

cmake -DGEOS_BUILD_STATIC=on -DGEOS_BUILD_SHARED=off ..

it fails with the error:

CMake Error at capi/CMakeLists.txt:45 (add_dependencies):
  Cannot add target-level dependencies to non-existent target "geos_c".

  The add_dependencies works for top-level logical targets created by the
  add_executable, add_library, or add_custom_target commands.  If you want to
  add file-level dependencies see the DEPENDS option of the add_custom_target
  and add_custom_command commands.

The provided patch makes it optional to build C API (on by default, as in master), and static library builds fine.

The geos version is 3.7.0

[basiliscos]

CMakeLists patch to optionally build C API

[basiliscos]

With the patch it is possible to configure CMake as

cmake -DGEOS_BUILD_STATIC=on -DGEOS_BUILD_SHARED=off -DGEOS_BUILD_CAPI=off ..

[pramsey]

cmake has changed a lot since this ticket, and I find that cmake -DBUILD_SHARED_LIBS=OFF builds a libgeos.a just fine.

[GitHub <noreply@…>]

In 87bf94a/git:

Fix CMake on Windows with Visual Studio (#945)

Avoid setting CMAKE_BUILD_TYPE default when multi-config generators are
used.

Avoid setting CMAKE_BUILD_TYPE STRINGS property if it is not a cache
variable. This avoids CMake errors if CMAKE_BUILD_TYPE isn't set on the
command-line.

Closes #932

[Mike Taves <mwtoews@…>]

In 40da3a61/git:

Fix CMake on Windows with Visual Studio (#945)

Avoid setting CMAKE_BUILD_TYPE default when multi-config generators are
used.

Avoid setting CMAKE_BUILD_TYPE STRINGS property if it is not a cache
variable. This avoids CMake errors if CMAKE_BUILD_TYPE isn't set on the
command-line.

Closes #932