Collapse arbor-sim#2390 into this and guard installation behing flag.

CMakeLists.txt

@@ -296,24 +296,23 @@ else()
     endif()
 endif()
 
+add_subdirectory(ext)
+install(TARGETS ext-hwloc EXPORT arbor-targets)
+install(TARGETS ext-random123 EXPORT arbor-targets)
+target_link_libraries(arbor-public-deps INTERFACE ext-units)
+install(TARGETS compile_flags_target EXPORT arbor-targets)
+
 add_library(ext-units INTERFACE)
 if(ARB_USE_BUNDLED_UNITS)
     target_link_libraries(ext-units INTERFACE units::units)
+    install(TARGETS ext-units units EXPORT arbor-targets)
 else()
     find_package(units REQUIRED)
     target_link_directories(ext-units INTERFACE ${units_LIBRARY_DIRS})
     target_link_libraries(ext-units INTERFACE ${units_LIBRARY})
     target_include_directories(ext-units INTERFACE ${units_INCLUDE_DIR})
 endif()
 
-
-add_subdirectory(ext)
-install(TARGETS ext-hwloc EXPORT arbor-targets)
-install(TARGETS ext-random123 EXPORT arbor-targets)
-target_link_libraries(arbor-public-deps INTERFACE ext-units)
-install(TARGETS ext-units EXPORT arbor-targets)
-install(TARGETS units compile_flags_target EXPORT arbor-targets)
-
 # Keep track of packages we need to add to the generated CMake config
 # file for arbor.
 

ext/CMakeLists.txt

@@ -126,7 +126,7 @@ if (ARB_USE_BUNDLED_UNITS)
     set(UNITS_BUILD_CONVERTER_APP OFF CACHE INTERNAL "")
     set(UNITS_BUILD_WEBSERVER OFF CACHE INTERNAL "")
     set(UNITS_INSTALL ON CACHE INTERNAL "")
-    # set(UNITS_NAMESPACE "llnl::units" CACHE INTERNAL "")
+    set(UNITS_BINARY_ONLY_INSTALL ON CACHE INTERNAL "")
 
     add_subdirectory("${PROJECT_SOURCE_DIR}/ext/units" "${PROJECT_BINARY_DIR}/ext/units")