build: Introduce "Kernel" installation component

This change enables building and installing only `libbitcoinkernel`,
without the need to disable other targets during the project build
system generation.

Author: hebasto

src/kernel/CMakeLists.txt

@@ -100,7 +100,13 @@ set_target_properties(bitcoinkernel PROPERTIES
 
 include(GNUInstallDirs)
 install(TARGETS bitcoinkernel
-  RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
-  LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
-  ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+  RUNTIME
+    DESTINATION ${CMAKE_INSTALL_BINDIR}
+    COMPONENT Kernel
+  LIBRARY
+    DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    COMPONENT Kernel
+  ARCHIVE
+    DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    COMPONENT Kernel
 )