find_program: Consider CWD only for paths with separator

find_program() incorrectly prepended search path components
to absolute file paths, and incorrectly searched the current
working directory for files that contained no directory
separators.

* Replace calls cmFindProgramHelper::CheckDirectory(std::string())
  with call of new method cmFindProgramHelper::CheckCompoundNames()
  that checks for the presence of a directory separator in the
  file name.
* Use cmSystemTools::CollapseCombinedPath rather than string
  concatenation to properly combine absolute file names with
  search path components.
* Add unit tests to verify corrections.

Fixes: #18044

1 files changed, 1 insertions, 0 deletions

diff --git a/Tests/RunCMake/find_program/testCWD b/Tests/RunCMake/find_program/testCWD
new file mode 100755
index 0000000..1a24852
--- /dev/null
+++ b/Tests/RunCMake/find_program/testCWD
@@ -0,0 +1 @@
+#!/bin/sh