GetPrerequisites: join if() clauses

These all test the same variable for different values, so only one of them can
ever be true. This also allows to completely remove one variable that only
flagged if one of the conditions matched.

Modules/GetPrerequisites.cmake

@@ -666,45 +666,31 @@ function(get_prerequisites target prerequisites_var exclude_system recurse exepa
     return()
   endif()
 
-  set(gp_tool_known 0)
-
   if(gp_tool STREQUAL "ldd")
     set(gp_cmd_args "")
     set(gp_regex "^[\t ]*[^\t ]+ => ([^\t\(]+) .*${eol_char}$")
     set(gp_regex_error "not found${eol_char}$")
     set(gp_regex_fallback "^[\t ]*([^\t ]+) => ([^\t ]+).*${eol_char}$")
     set(gp_regex_cmp_count 1)
-    set(gp_tool_known 1)
-  endif()
-
-  if(gp_tool STREQUAL "otool")
+  elseif(gp_tool STREQUAL "otool")
     set(gp_cmd_args "-L")
     set(gp_regex "^\t([^\t]+) \\(compatibility version ([0-9]+.[0-9]+.[0-9]+), current version ([0-9]+.[0-9]+.[0-9]+)\\)${eol_char}$")
     set(gp_regex_error "")
     set(gp_regex_fallback "")
     set(gp_regex_cmp_count 3)
-    set(gp_tool_known 1)
-  endif()
-
-  if(gp_tool STREQUAL "dumpbin")
+  elseif(gp_tool STREQUAL "dumpbin")
     set(gp_cmd_args "/dependents")
     set(gp_regex "^    ([^ ].*[Dd][Ll][Ll])${eol_char}$")
     set(gp_regex_error "")
     set(gp_regex_fallback "")
     set(gp_regex_cmp_count 1)
-    set(gp_tool_known 1)
-  endif()
-
-  if(gp_tool STREQUAL "objdump")
+  elseif(gp_tool STREQUAL "objdump")
     set(gp_cmd_args "-p")
     set(gp_regex "^\t*DLL Name: (.*\\.[Dd][Ll][Ll])${eol_char}$")
     set(gp_regex_error "")
     set(gp_regex_fallback "")
     set(gp_regex_cmp_count 1)
-    set(gp_tool_known 1)
-  endif()
-
-  if(NOT gp_tool_known)
+  else()
     message(STATUS "warning: gp_tool='${gp_tool}' is an unknown tool...")
     message(STATUS "CMake function get_prerequisites needs more code to handle '${gp_tool}'")
     message(STATUS "Valid gp_tool values are dumpbin, ldd, objdump and otool.")