cmake: add BUILD_SHARED_LIBS option

Linux distributions like Fedora and OpenSUSE build gdb against a static
libipt, which is obtained by patching libipt/CMakeLists.txt:
...
-add_library(libipt SHARED
+add_library(libipt STATIC
...

Add option BUILD_SHARED_LIBS that can be used to build a static instead of a
shared library:
...
$ cmake $src -DBUILD_SHARED_LIBS=OFF
...

Signed-off-by: Tom de Vries <tdevries@suse.de>
3 files changed