Tests: Fix `file://` URLs given to curl

Since upstream curl commit curl-7_52_0~131 (URL-parser: for
file://[host]/ URLs, the [host] must be localhost, 2016-11-11) we can no
longer use URLs of the form `file://c:/...` on Windows.  These worked
only accidentally before.  Use `file:///c:/...` instead.

Tests/CMakeTests/FileDownloadBadHashTest.cmake.in

@@ -1,4 +1,7 @@
-set(url "file://@CMAKE_CURRENT_SOURCE_DIR@/FileDownloadInput.png")
+if(NOT "@CMAKE_CURRENT_SOURCE_DIR@" MATCHES "^/")
+  set(slash /)
+endif()
+set(url "file://${slash}@CMAKE_CURRENT_SOURCE_DIR@/FileDownloadInput.png")
 set(dir "@CMAKE_CURRENT_BINARY_DIR@/downloads")
 
 file(DOWNLOAD

Tests/CMakeTests/FileDownloadTest.cmake.in

@@ -1,4 +1,7 @@
-set(url "file://@CMAKE_CURRENT_SOURCE_DIR@/FileDownloadInput.png")
+if(NOT "@CMAKE_CURRENT_SOURCE_DIR@" MATCHES "^/")
+  set(slash /)
+endif()
+set(url "file://${slash}@CMAKE_CURRENT_SOURCE_DIR@/FileDownloadInput.png")
 set(dir "@CMAKE_CURRENT_BINARY_DIR@/downloads")
 
 message(STATUS "FileDownload:1")

Tests/CMakeTests/FileUploadTest.cmake.in

@@ -10,7 +10,10 @@ endif()
 file(MAKE_DIRECTORY "@CMAKE_CURRENT_BINARY_DIR@/uploads")
 
 set(filename "@CMAKE_CURRENT_SOURCE_DIR@/FileDownloadInput.png")
-set(urlbase "file://@CMAKE_CURRENT_BINARY_DIR@/uploads")
+if(NOT "@CMAKE_CURRENT_BINARY_DIR@" MATCHES "^/")
+  set(slash /)
+endif()
+set(urlbase "file://${slash}@CMAKE_CURRENT_BINARY_DIR@/uploads")
 
 message(STATUS "FileUpload:1")
 file(UPLOAD

Tests/RunCMake/file/DOWNLOAD-hash-mismatch.cmake

@@ -1,5 +1,8 @@
+if(NOT "${CMAKE_CURRENT_SOURCE_DIR}" MATCHES "^/")
+  set(slash /)
+endif()
 file(DOWNLOAD
-  "file://${CMAKE_CURRENT_SOURCE_DIR}/DOWNLOAD-hash-mismatch.txt"
+  "file://${slash}${CMAKE_CURRENT_SOURCE_DIR}/DOWNLOAD-hash-mismatch.txt"
   ${CMAKE_CURRENT_BINARY_DIR}/hash-mismatch.txt
   EXPECTED_HASH SHA1=0123456789abcdef0123456789abcdef01234567
   STATUS status

Tests/RunCMake/file/DOWNLOAD-unused-argument.cmake

@@ -1,5 +1,8 @@
+if(NOT "${CMAKE_CURRENT_SOURCE_DIR}" MATCHES "^/")
+  set(slash /)
+endif()
 file(DOWNLOAD
-  "file://${CMAKE_CURRENT_SOURCE_DIR}/DOWNLOAD-unused-argument.txt"
+  "file://${slash}${CMAKE_CURRENT_SOURCE_DIR}/DOWNLOAD-unused-argument.txt"
   "${CMAKE_CURRENT_BINARY_DIR}/unused-argument.txt"
   JUNK
   )

Tests/RunCMake/file/UPLOAD-unused-argument.cmake

@@ -1,5 +1,8 @@
+if(NOT "${CMAKE_CURRENT_BINARY_DIR}" MATCHES "^/")
+  set(slash /)
+endif()
 file(UPLOAD
   "${CMAKE_CURRENT_SOURCE_DIR}/UPLOAD-unused-argument.txt"
-  "file://${CMAKE_CURRENT_BINARY_DIR}/unused-argument.txt"
+  "file://${slash}${CMAKE_CURRENT_BINARY_DIR}/unused-argument.txt"
   JUNK
   )