Allow OBJECT libraries to be installed, exported, and imported

Teach install() and export() to handle the actual object files.
Disallow this on Xcode with multiple architectures because it
still cannot be cleanly supported there.

Co-Author: Brad King <brad.king@kitware.com>

Tests/RunCMake/ObjectLibrary/Export-stderr.txt

@@ -1,4 +0,0 @@
-CMake Error at Export.cmake:2 \(export\):
-  export given OBJECT library "A" which may not be exported.
-Call Stack \(most recent call first\):
-  CMakeLists.txt:3 \(include\)

Tests/RunCMake/ObjectLibrary/ExportNotSupported-stderr.txt

@@ -0,0 +1,5 @@
+CMake Error at ExportNotSupported.cmake:[0-9]+ \(export\):
+  export given OBJECT library "A" which may not be exported under Xcode with
+  multiple architectures.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)

Tests/RunCMake/ObjectLibrary/ExportNotSupported.cmake

@@ -0,0 +1,2 @@
+add_library(A OBJECT a.c)
+export(TARGETS A FILE AExport.cmake)

Tests/RunCMake/ObjectLibrary/Import.cmake

@@ -1 +1,12 @@
+
 add_library(A OBJECT IMPORTED)
+
+# We don't actually build this example so just configure dummy
+# object files to test.  They do not have to exist.
+set_property(TARGET A APPEND PROPERTY IMPORTED_CONFIGURATIONS DEBUG)
+set_target_properties(A PROPERTIES
+  IMPORTED_OBJECTS_DEBUG "${CMAKE_CURRENT_BINARY_DIR}/does_not_exist.o"
+  IMPORTED_OBJECTS "${CMAKE_CURRENT_BINARY_DIR}/does_not_exist.o"
+  )
+
+add_library(B $<TARGET_OBJECTS:A> b.c)

Tests/RunCMake/ObjectLibrary/ImportNotSupported-stderr.txt

@@ -1,4 +1,5 @@
-CMake Error at Import.cmake:1 \(add_library\):
-  The OBJECT library type may not be used for IMPORTED libraries.
+CMake Error at ImportNotSupported.cmake:[0-9]+ \(add_library\):
+  The OBJECT library type may not be used for IMPORTED libraries under Xcode
+  with multiple architectures.
 Call Stack \(most recent call first\):
   CMakeLists.txt:3 \(include\)

Tests/RunCMake/ObjectLibrary/ImportNotSupported.cmake

@@ -0,0 +1 @@
+add_library(A OBJECT IMPORTED)

Tests/RunCMake/ObjectLibrary/InstallNotSupported-stderr.txt

@@ -1,4 +1,5 @@
-CMake Error at Install.cmake:2 \(install\):
-  install TARGETS given OBJECT library "A" which may not be installed.
+CMake Error at InstallNotSupported.cmake:[0-9]+ \(install\):
+  install TARGETS given OBJECT library "A" which may not be installed under
+  Xcode with multiple architectures.
 Call Stack \(most recent call first\):
   CMakeLists.txt:3 \(include\)

Tests/RunCMake/ObjectLibrary/InstallNotSupported.cmake

@@ -0,0 +1,2 @@
+add_library(A OBJECT a.c)
+install(TARGETS A DESTINATION lib)

Tests/RunCMake/ObjectLibrary/RunCMakeTest.cmake

@@ -5,9 +5,15 @@ run_cmake(BadSourceExpression2)
 run_cmake(BadSourceExpression3)
 run_cmake(BadObjSource1)
 run_cmake(BadObjSource2)
-run_cmake(Export)
-run_cmake(Import)
-run_cmake(Install)
+if(RunCMake_GENERATOR STREQUAL "Xcode" AND "$ENV{CMAKE_OSX_ARCHITECTURES}" MATCHES "[;$]")
+  run_cmake(ExportNotSupported)
+  run_cmake(ImportNotSupported)
+  run_cmake(InstallNotSupported)
+else()
+  run_cmake(Export)
+  run_cmake(Import)
+  run_cmake(Install)
+endif()
 run_cmake(LinkObjLHS)
 run_cmake(LinkObjRHS1)
 run_cmake(LinkObjRHS2)

Tests/RunCMake/ObjectLibrary/b.c

@@ -0,0 +1,4 @@
+int b(void)
+{
+  return 0;
+}