build error (and suggested fix): add ARCHIVE DESTINATION for static libs

[geoffthorpe]

In my environment I hit build errors with the following two lines of CMakeLists.txt;

s2argv-execs/CMakeLists.txt

Lines 34 to 35 in 40f86a2

	install(TARGETS execs_static LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})
	install(TARGETS execs-embedded_static LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})

For those two targets (the only ones declared as static libraries), it seems cmake needed ARCHIVE DESTINATION, in addition to (or instead of) LIBRARY DESTINATION.

The following local change allows the build to complete successfully;

 install(TARGETS execs LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})
 install(TARGETS execs-embedded LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})
-install(TARGETS execs_static LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})
-install(TARGETS execs-embedded_static LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})
+install(TARGETS execs_static LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+       ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
+install(TARGETS execs-embedded_static LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+       ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
 install(FILES execs.h DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})