tests: Extend tests that use Threads internally to set method

It turns out there's a bug in creating a sub dependency out of threads
in that we pass all of the kwargs from the parent to the
ThreadDependency instance. This demonstrates the bug.

test cases/frameworks/15 llvm/meson.build

@@ -1,6 +1,6 @@
 project('llvmtest', ['c', 'cpp'], default_options : ['c_std=c99'])
 
-d = dependency('llvm', required : false)
+d = dependency('llvm', required : false, method : 'config-tool')
 if not d.found()
   d = dependency('llvm', required : false, static : true)
   if not d.found()

test cases/frameworks/2 gtest/meson.build

@@ -4,7 +4,7 @@ gtest = dependency('gtest', main : true, required : false)
 if not gtest.found()
   error('MESON_SKIP_TEST: gtest not installed.')
 endif
-gtest_nomain = dependency('gtest', main : false)
+gtest_nomain = dependency('gtest', main : false, method : 'system')
 
 e = executable('testprog', 'test.cc', dependencies : gtest)
 test('gtest test', e)

test cases/frameworks/3 gmock/meson.build

@@ -3,7 +3,7 @@ project('gmock test', 'cpp')
 # Using gmock without gtest is a pain so just
 # don't support that then.
 
-gtest = dependency('gtest', main : true, required : false)
+gtest = dependency('gtest', main : true, required : false, method : 'system')
 if not gtest.found()
   error('MESON_SKIP_TEST: gtest not installed.')
 endif