external: Use sub-Make for external projects.

Use sub-Make for external projects so they can reuse the make jobserver.

This removes the restriction to have only one job for some external projects. Instead now they should reuse the processes used for the main build.

(Note: These changes, with similar fixes in flesnet, reduced the compile time for flesnet in CbmRoot from ~2m30s to ~1m on my machine.)

external/InstallFlesnet.cmake

@@ -3,7 +3,7 @@
 # The included libraries provide the interface to the experiment data in timeslices
 # both online and in timeslice archive (.tsa) files.
 
-set(FLESNET_VERSION 0529b038b2c2c8d9b82580e0d080a6abc2ef199f) # 2023-07-18
+set(FLESNET_VERSION e553a5fbd4d1ccc2c55ea11632c38f24516b8461) # 2023-10-12
 
 set(FLESNET_SRC_URL "https://github.com/cbm-fles/flesnet")
 
@@ -31,6 +31,12 @@ if(APPLE)
                  )
 endif()
 
+if ("${CMAKE_GENERATOR}" MATCHES "Make")
+  set(FLESNET_BUILD_COMMAND "$(MAKE)")
+else()
+  set(FLESNET_BUILD_COMMAND "${CMAKE_COMMAND} --build . --target")
+endif()
+
 ExternalProject_Add(
   flesnet
   SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/flesnet
@@ -43,7 +49,7 @@ ExternalProject_Add(
              ${CMAKE_CURRENT_SOURCE_DIR}/flesnet
   BUILD_IN_SOURCE 0
   LOG_DOWNLOAD 1 LOG_CONFIGURE 1 LOG_BUILD 1 LOG_INSTALL 1
-  BUILD_COMMAND ${CMAKE_COMMAND} --build . -j 1 --target logging monitoring fles_ipc
+  BUILD_COMMAND ${FLESNET_BUILD_COMMAND} logging monitoring fles_ipc
   BUILD_BYPRODUCTS ${FLESNET_DESTDIR}/src/flesnet-build/lib/fles_ipc/${CMAKE_STATIC_LIBRARY_PREFIX}fles_ipc${CMAKE_STATIC_LIBRARY_SUFFIX}
   INSTALL_COMMAND ""
 )
@@ -93,7 +99,6 @@ endif()
 list(APPEND dir_to_link
      ${FLESNET_DESTDIR}/src/flesnet-build/lib/logging/${CMAKE_STATIC_LIBRARY_PREFIX}logging${CMAKE_STATIC_LIBRARY_SUFFIX}
      ${FLESNET_DESTDIR}/src/flesnet-build/lib/monitoring/${CMAKE_STATIC_LIBRARY_PREFIX}monitoring${CMAKE_STATIC_LIBRARY_SUFFIX}
-     ${FLESNET_DESTDIR}/src/flesnet-build/_deps/fmtlib-build/${CMAKE_STATIC_LIBRARY_PREFIX}fmt${CMAKE_STATIC_LIBRARY_SUFFIX}
      )
 list(APPEND dir_to_link
      ${Boost_LOG_LIBRARY}
@@ -102,7 +107,8 @@ list(APPEND dir_to_link
      ${Boost_SERIALIZATION_LIBRARY}
      ${Boost_ASIO_LIBRARY}
      ${Boost_BEAST_LIBRARY}
-    )
+     fmt::fmt
+     )
 if(NOT APPLE)
   list(APPEND dir_to_link ${Boost_THREAD_LIBRARY} -lrt)
 endif()