GUI: Add install target for epee

contrib/epee/src/CMakeLists.txt

@@ -27,3 +27,13 @@
 # THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 add_library(epee STATIC http_auth.cpp mlog.cpp)
+# Build and install libepee if we're building for GUI
+if (BUILD_GUI_DEPS)
+    if(IOS)
+        set(lib_folder lib-${ARCH})
+    else()
+        set(lib_folder lib)
+    endif()
+    install(TARGETS epee
+        ARCHIVE DESTINATION ${lib_folder})
+endif()