Edit meson scripts to compile for Android

meson.build

@@ -17,6 +17,8 @@ pymod = import('python')
 python = pymod.find_installation('python3', required: true)
 
 cc = meson.get_compiler('cpp')
+lib_dir = meson.current_source_dir() / 'thirdparty/lib' / host_machine.system() / host_machine.cpu()
+inc_dir = 'thirdparty/include' / host_machine.system()
 
 global_cpp_defs = [
   '-DSPLIT_SAVES',
@@ -28,13 +30,21 @@ global_cpp_defs = [
   '-DDEBUG',
 ]
 
-if host_machine.system() == 'linux'
+if host_machine.system() == 'linux' or host_machine.system() == 'android'
   global_cpp_defs += ['-Dlinux', '-D__linux', '-D__linux__']
 endif
 
+if host_machine.system() == 'android'
+  global_cpp_defs += ['-D__android__']
+endif
+
 if get_option('renderer') == 'gles'
   global_cpp_defs += ['-DGLES']
-  gl_dep = dependency('glesv2', required: true)
+  if host_machine.system() == 'android'
+    gl_dep = cc.find_library('GLESv3', required: true )
+  else
+    gl_dep = dependency('glesv2', required: true)
+  endif
   glu_dep = dependency('', required: false)
 else
   gl_dep = dependency('gl', required: true)
@@ -69,10 +79,21 @@ global_cpp_args = [
 ]
 add_project_arguments(global_cpp_args, language: 'cpp')
 
-sdl2_dep = dependency('sdl2')
+if host_machine.system() == 'android'
+  sdl2_dep = declare_dependency(
+    dependencies: cc.find_library('SDL2', dirs: lib_dir, required: true ), 
+    include_directories: inc_dir)
+else
+  sdl2_dep = dependency('sdl2')
+endif
 thread_dep = dependency('threads')
 dl_dep = cc.find_library('dl', required: true)
-glm_dep = dependency('glm')
+
+if host_machine.system() == 'android'
+  glm_dep  = declare_dependency(include_directories: inc_dir)
+else
+  glm_dep = dependency('glm')
+endif
 
 stb = subproject('stb').get_variable('stb_inc')
 stb_dep = declare_dependency(include_directories: stb)