Drop find_(library|file|path) prefixes from PATH on non-Windows

Since commit v3.3.0-rc1~430^2 (Teach find_(library|file|path) to get
prefixes from PATH, 2015-02-18) we search in <prefix>/include and
<prefix>/lib directories for prefixes with bin directories in the PATH
environment variable.  The motivation was to support MSYS, MinGW and
similar Windows platforms in their default environments automatically.
At the time this behavior was thought to be worthwhile in general.

Suggested-by: Chuck Atkins <chuck.atkins@kitware.com>

Help/command/find_file.rst

@@ -14,7 +14,8 @@ find_file
 .. |CMAKE_XXX_PATH| replace:: :variable:`CMAKE_INCLUDE_PATH`
 .. |CMAKE_XXX_MAC_PATH| replace:: :variable:`CMAKE_FRAMEWORK_PATH`
 
-.. |SYSTEM_ENVIRONMENT_PATH_XXX| replace:: Directories in ``INCLUDE``,
+.. |SYSTEM_ENVIRONMENT_PATH_XXX| replace:: Directories in ``INCLUDE``.
+   On Windows hosts:
    ``<prefix>/include/<arch>`` if :variable:`CMAKE_LIBRARY_ARCHITECTURE`
    is set, and |SYSTEM_ENVIRONMENT_PREFIX_PATH_XXX_SUBDIR|, and the
    directories in ``PATH`` itself.

Help/command/find_library.rst

@@ -14,7 +14,8 @@ find_library
 .. |CMAKE_XXX_PATH| replace:: :variable:`CMAKE_LIBRARY_PATH`
 .. |CMAKE_XXX_MAC_PATH| replace:: :variable:`CMAKE_FRAMEWORK_PATH`
 
-.. |SYSTEM_ENVIRONMENT_PATH_XXX| replace:: Directories in ``LIB``,
+.. |SYSTEM_ENVIRONMENT_PATH_XXX| replace:: Directories in ``LIB``.
+   On Windows hosts:
    ``<prefix>/lib/<arch>`` if :variable:`CMAKE_LIBRARY_ARCHITECTURE` is set,
    and |SYSTEM_ENVIRONMENT_PREFIX_PATH_XXX_SUBDIR|,
    and the directories in ``PATH`` itself.

Help/command/find_path.rst

@@ -14,7 +14,8 @@ find_path
 .. |CMAKE_XXX_PATH| replace:: :variable:`CMAKE_INCLUDE_PATH`
 .. |CMAKE_XXX_MAC_PATH| replace:: :variable:`CMAKE_FRAMEWORK_PATH`
 
-.. |SYSTEM_ENVIRONMENT_PATH_XXX| replace:: Directories in ``INCLUDE``,
+.. |SYSTEM_ENVIRONMENT_PATH_XXX| replace:: Directories in ``INCLUDE``.
+   On Windows hosts:
    ``<prefix>/include/<arch>`` if :variable:`CMAKE_LIBRARY_ARCHITECTURE`
    is set, and |SYSTEM_ENVIRONMENT_PREFIX_PATH_XXX_SUBDIR|, and the
    directories in ``PATH`` itself.

Help/release/dev/find-command-prefix-from-PATH-windows-only.rst

@@ -0,0 +1,12 @@
+find-command-prefix-from-PATH-windows-only
+------------------------------------------
+
+* The :command:`find_library`, :command:`find_path`, and :command:`find_file`
+  commands no longer search in installation prefixes derived from the ``PATH``
+  environment variable on non-Windows platforms.  This behavior was added in
+  CMake 3.3 to support Windows hosts but has proven problematic on UNIX hosts.
+  Users that keep some ``<prefix>/bin`` directories in the ``PATH`` just for
+  their tools do not necessarily want any supporting ``<prefix>/lib``
+  directories searched.  One may set the ``CMAKE_PREFIX_PATH`` environment
+  variable with a :ref:`;-list <CMake Language Lists>` of prefixes that are
+  to be searched.

Source/cmFindBase.cxx

@@ -276,10 +276,16 @@ void cmFindBase::FillSystemEnvironmentPath()
   if(!this->EnvironmentPath.empty())
     {
     paths.AddEnvPath(this->EnvironmentPath);
+#if defined(_WIN32) || defined(__CYGWIN__)
     paths.AddEnvPrefixPath("PATH", true);
+    paths.AddEnvPath("PATH");
+#endif
     }
+  else
+    {
     // Add PATH
     paths.AddEnvPath("PATH");
+    }
   paths.AddSuffixes(this->SearchPathSuffixes);
 }
 

Tests/RunCMake/find_file/RunCMakeTest.cmake

@@ -1,3 +1,5 @@
 include(RunCMake)
 
+if(WIN32 OR CYGWIN)
   run_cmake(PrefixInPATH)
+endif()

Tests/RunCMake/find_library/RunCMakeTest.cmake

@@ -1,4 +1,6 @@
 include(RunCMake)
 
 run_cmake(Created)
+if(WIN32 OR CYGWIN)
   run_cmake(PrefixInPATH)
+endif()

Tests/RunCMake/find_path/RunCMakeTest.cmake

@@ -1,3 +1,5 @@
 include(RunCMake)
 
+if(WIN32 OR CYGWIN)
   run_cmake(PrefixInPATH)
+endif()