ExternalProject: Add options to specify BYPRODUCTS (#14963)

The external project's build process may generate byproducts on which
other rules in the driving project's build later depend.  Provide a way
for the driving project to specify what byproducts it expects to be made
available by the custom commands that drive the external project.

1 files changed, 13 insertions, 0 deletions

diff --git a/Modules/ExternalProject.cmake b/Modules/ExternalProject.cmake
index 32f6d2c..e5616b1 100644
--- a/Modules/ExternalProject.cmake
+++ b/Modules/ExternalProject.cmake
@@ -132,6 +132,9 @@ Create custom targets to build projects in external trees
     Use source dir for build dir
   ``BUILD_ALWAYS 1``
     No stamp file, build step always runs
+  ``BUILD_BYPRODUCTS <file>...``
+    Files that will be generated by the build command but may or may
+    not have their modification time updated by subsequent builds.
 
   Install step options are:
 
@@ -234,6 +237,9 @@ Create custom targets to build projects in external trees
     Steps that depend on this step
   ``DEPENDS <file>...``
     Files on which this step depends
+  ``BYPRODUCTS <file>...``
+    Files that will be generated by this step but may or may not
+    have their modification time updated by subsequent builds.
   ``ALWAYS 1``
     No stamp file, step always runs
   ``EXCLUDE_FROM_MAIN 1``
@@ -1409,6 +1415,9 @@ function(ExternalProject_Add_Step name step)
   # Dependencies on files.
   get_property(depends TARGET ${name} PROPERTY _EP_${step}_DEPENDS)
 
+  # Byproducts of the step.
+  get_property(byproducts TARGET ${name} PROPERTY _EP_${step}_BYPRODUCTS)
+
   # Dependencies on steps.
   get_property(dependees TARGET ${name} PROPERTY _EP_${step}_DEPENDEES)
   foreach(dependee IN LISTS dependees)
@@ -1466,6 +1475,7 @@ function(ExternalProject_Add_Step name step)
 
   add_custom_command(
     OUTPUT ${stamp_file}
+    BYPRODUCTS ${byproducts}
     COMMENT ${comment}
     COMMAND ${command}
     COMMAND ${touch}
@@ -2139,8 +2149,11 @@ function(_ep_add_build_command name)
     set(always 0)
   endif()
 
+  get_property(build_byproducts TARGET ${name} PROPERTY _EP_BUILD_BYPRODUCTS)
+
   ExternalProject_Add_Step(${name} build
     COMMAND ${cmd}
+    BYPRODUCTS ${build_byproducts}
     WORKING_DIRECTORY ${binary_dir}
     DEPENDEES configure
     ALWAYS ${always}