ExternalProject: Fix cache generation when args end with "-NOTFOUND"

Generalize the fix in commit v3.11.0-rc4~8^2 (ExternalProject: Fix cache
generation when last args ends with "-NOTFOUND", 2018-03-10) to work for
any argument rather than just the last one.

ExternalProject can now successfully generate the cache file when any
(not only the last one) cache variable associated with either
`CMAKE_CACHE_ARGS` or `CMAKE_DEFAULT_CACHE_ARGS` configure step option
is set to a `<value>` ending with `-NOTFOUND`.

Modules/ExternalProject.cmake

@@ -1686,7 +1686,7 @@ function(_ep_command_line_to_initial_cache var args force)
   foreach(line ${args})
     if("${line}" MATCHES "^-D(.*)")
       set(line "${CMAKE_MATCH_1}")
-      if(setArg)
+      if(NOT "${setArg}" STREQUAL "")
         # This is required to build up lists in variables, or complete an entry
         string(APPEND setArg "${accumulator}\" CACHE ${type} \"Initial cache\" ${forceArg})")
         string(APPEND script_initial_cache "\n${setArg}")

Tests/RunCMake/ExternalProject/CMAKE_CACHE_ARGS-check.cmake

@@ -33,3 +33,12 @@ if(NOT "${CMAKE_MATCH_0}" MATCHES FORCE)
   set(RunCMake_TEST_FAILED "Expected forced TEST_OPTIONAL argument")
   return()
 endif()
+
+if(NOT "${_cache}" MATCHES "set\\(TEST_OPTIONAL_LAST \"TEST_OPTIONAL_LAST-NOTFOUND\".+\\)")
+  set(RunCMake_TEST_FAILED "Cannot find TEST_OPTIONAL_LAST argument in cache")
+  return()
+endif()
+if(NOT "${CMAKE_MATCH_0}" MATCHES FORCE)
+  set(RunCMake_TEST_FAILED "Expected forced TEST_OPTIONAL_LAST argument")
+  return()
+endif()

Tests/RunCMake/ExternalProject/CMAKE_CACHE_ARGS.cmake

@@ -9,4 +9,5 @@ ExternalProject_Add(FOO TMP_DIR "${CMAKE_CURRENT_BINARY_DIR}/tmp"
                         CMAKE_CACHE_ARGS
                             "-DFOO:STRING=$<1:BAR>$<0:BAD>"
                             "-DTEST_LIST:STRING=A;B;C"
-                            "-DTEST_OPTIONAL:FILEPATH=TEST_OPTIONAL-NOTFOUND")
+                            "-DTEST_OPTIONAL:FILEPATH=TEST_OPTIONAL-NOTFOUND"
+                            "-DTEST_OPTIONAL_LAST:FILEPATH=TEST_OPTIONAL_LAST-NOTFOUND")

Tests/RunCMake/ExternalProject/CMAKE_CACHE_DEFAULT_ARGS-check.cmake

@@ -33,3 +33,12 @@ if("${CMAKE_MATCH_0}" MATCHES FORCE)
   set(RunCMake_TEST_FAILED "Expected not forced TEST_OPTIONAL argument")
   return()
 endif()
+
+if(NOT "${_cache}" MATCHES "set\\(TEST_OPTIONAL_LAST \"TEST_OPTIONAL_LAST-NOTFOUND\".+\\)")
+  set(RunCMake_TEST_FAILED "Cannot find TEST_OPTIONAL_LAST argument in cache")
+  return()
+endif()
+if("${CMAKE_MATCH_0}" MATCHES FORCE)
+  set(RunCMake_TEST_FAILED "Expected not forced TEST_OPTIONAL_LAST argument")
+  return()
+endif()

Tests/RunCMake/ExternalProject/CMAKE_CACHE_DEFAULT_ARGS.cmake

@@ -9,4 +9,5 @@ ExternalProject_Add(FOO TMP_DIR "${CMAKE_CURRENT_BINARY_DIR}/tmp"
                         CMAKE_CACHE_DEFAULT_ARGS
                             "-DFOO:STRING=$<1:BAR>$<0:BAD>"
                             "-DTEST_LIST:STRING=A;B;C"
-                            "-DTEST_OPTIONAL:FILEPATH=TEST_OPTIONAL-NOTFOUND")
+                            "-DTEST_OPTIONAL:FILEPATH=TEST_OPTIONAL-NOTFOUND"
+                            "-DTEST_OPTIONAL_LAST:FILEPATH=TEST_OPTIONAL_LAST-NOTFOUND")