build: Bump C++ standard requirement to C++14 to fix FTBFS with LLVM 10

When building Mesa against a recent LLVM 10 with C++11, the build fails
if the AMD common code is built as well due to "std::index_sequence"
being undeclared.

LLVM requires a minimum of C++14.

Signed-off-by: Kai Wasserbäch <kai@dev.carbon-project.org>
Acked-by: Eric Engestrom <eric@engestrom.ch>

meson.build

@@ -26,7 +26,7 @@ project(
   ).stdout(),
   license : 'MIT',
   meson_version : '>= 0.46',
-  default_options : ['buildtype=debugoptimized', 'b_ndebug=if-release', 'c_std=c99', 'cpp_std=c++11']
+  default_options : ['buildtype=debugoptimized', 'b_ndebug=if-release', 'c_std=c99', 'cpp_std=c++14']
 )
 
 cc = meson.get_compiler('c')

scons/llvm.py

@@ -269,7 +269,7 @@ def generate(env):
             env.ParseConfig('%s --ldflags' % llvm_config)
             if llvm_version >= distutils.version.LooseVersion('3.5'):
                 env.ParseConfig('%s --system-libs' % llvm_config)
-                env.Append(CXXFLAGS = ['-std=c++11'])
+                env.Append(CXXFLAGS = ['-std=c++14'])
         except OSError:
             print('scons: llvm-config version %s failed' % llvm_version)
             return

src/gallium/auxiliary/Android.mk

@@ -48,7 +48,7 @@ LOCAL_SRC_FILES += \
 $(call mesa-build-with-llvm)
 endif
 
-LOCAL_CPPFLAGS += -std=c++11
+LOCAL_CPPFLAGS += -std=c++14
 
 # We need libmesa_nir to get NIR's generated include directories.
 LOCAL_MODULE := libmesa_gallium

src/gallium/drivers/swr/SConscript

@@ -32,7 +32,7 @@ else:
 
 if not env['msvc'] :
     env.Append(CCFLAGS = [
-        '-std=c++11',
+        '-std=c++14',
     ])
 
 swrroot = '#src/gallium/drivers/swr/'