Unnecessary files from libshared are installed when used as submodule

[wshanks]

GothenburgBitFactory/timewarrior#706 changed from explicitly listing libshared source files to using add_subdirectory(${CMAKE_SOURCE_DIR}/src/libshared). This has the side effect of inheriting libshared's cmake install rules and causing files like lib/libshared.a and include/JSON.h to get installed along with bin/timew, etc.

I discovered these files while trying to make a conda package of timewarrior. For now, I am working around the issue by using this patch:

--- a/src/libshared/src/CMakeLists.txt
+++ b/src/libshared/src/CMakeLists.txt
@@ -56,10 +56,6 @@
 
 add_library (shared STATIC ${shared_SRCS})
 
-set (CMAKE_INSTALL_LIBDIR lib CACHE PATH "Output directory for libraries")
-install (TARGETS shared DESTINATION lib)
-install (FILES ${shared_HEADERS} DESTINATION include)
-
 add_executable (lex_executable lex.cpp)
 target_link_libraries (lex_executable shared)
 set_property (TARGET lex_executable PROPERTY OUTPUT_NAME "lex")