cmake(android): update CMAKE_FIND_ROOT_PATH_MODE_* handling

Avoids this error message with CMake 3.10:
CMake Error: CMake was unable to find a build program corresponding to "Ninja".
CMAKE_MAKE_PROGRAM is not set. You probably need to select a different build tool.

Related changes is that pkg-config tool is found (/usr/bin/pkg-config).

platforms/android/android.toolchain.cmake

@@ -1596,16 +1596,49 @@ set( CMAKE_FIND_ROOT_PATH
     "${CMAKE_INSTALL_PREFIX}/share" )
 
 # only search for libraries and includes in the ndk toolchain
-set( CMAKE_FIND_ROOT_PATH_MODE_PROGRAM ONLY )
-set( CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY )
-set( CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY )
+if(NOT CMAKE_FIND_ROOT_PATH_MODE_LIBRARY)
+  set( CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY )
+endif()
+
+if(NOT CMAKE_FIND_ROOT_PATH_MODE_INCLUDE)
+  set( CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY )
+endif()
+
+if(NOT CMAKE_FIND_ROOT_PATH_MODE_PACKAGE)
+  set( CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY )
+endif()
+
+if(NOT CMAKE_FIND_ROOT_PATH_MODE_PROGRAM)
+  set( CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER )
+endif()
+
+macro(__cmake_find_root_save_and_reset)
+  foreach(v
+      CMAKE_FIND_ROOT_PATH_MODE_LIBRARY
+      CMAKE_FIND_ROOT_PATH_MODE_INCLUDE
+      CMAKE_FIND_ROOT_PATH_MODE_PACKAGE
+      CMAKE_FIND_ROOT_PATH_MODE_PROGRAM
+  )
+    set(__save_${v} ${${v}})
+    set(${v} NEVER)
+  endforeach()
+endmacro()
 
+macro(__cmake_find_root_restore)
+  foreach(v
+      CMAKE_FIND_ROOT_PATH_MODE_LIBRARY
+      CMAKE_FIND_ROOT_PATH_MODE_INCLUDE
+      CMAKE_FIND_ROOT_PATH_MODE_PACKAGE
+      CMAKE_FIND_ROOT_PATH_MODE_PROGRAM
+  )
+    set(${v} ${__save_${v}})
+    unset(__save_${v})
+  endforeach()
+endmacro()
 
 # macro to find packages on the host OS
 macro( find_host_package )
- set( CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER )
- set( CMAKE_FIND_ROOT_PATH_MODE_LIBRARY NEVER )
- set( CMAKE_FIND_ROOT_PATH_MODE_INCLUDE NEVER )
+ __cmake_find_root_save_and_reset()
  if( CMAKE_HOST_WIN32 )
   SET( WIN32 1 )
   SET( UNIX )
@@ -1617,17 +1650,13 @@ macro( find_host_package )
  SET( WIN32 )
  SET( APPLE )
  SET( UNIX 1 )
- set( CMAKE_FIND_ROOT_PATH_MODE_PROGRAM ONLY )
- set( CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY )
- set( CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY )
+ __cmake_find_root_restore()
 endmacro()
 
 
 # macro to find programs on the host OS
 macro( find_host_program )
- set( CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER )
- set( CMAKE_FIND_ROOT_PATH_MODE_LIBRARY NEVER )
- set( CMAKE_FIND_ROOT_PATH_MODE_INCLUDE NEVER )
+ __cmake_find_root_save_and_reset()
  if( CMAKE_HOST_WIN32 )
   SET( WIN32 1 )
   SET( UNIX )
@@ -1639,9 +1668,7 @@ macro( find_host_program )
  SET( WIN32 )
  SET( APPLE )
  SET( UNIX 1 )
- set( CMAKE_FIND_ROOT_PATH_MODE_PROGRAM ONLY )
- set( CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY )
- set( CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY )
+ __cmake_find_root_restore()
 endmacro()