eaaf95f5c8
isysroot influences where clang will pick up libc++. Without this, and with
Xcode 14.3, cling will use libc++ from Xcode (or the command line tools) rather
than stdc++ from the macOS SDK, as clang would normally use. Passing the isysroot
(which point to the SDK) fixes this.
This solves build errors such as:
```
While building module 'Core':
While building module 'std' imported from input_line_1:1:
In file included from <module-includes>:17:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/math.h:309:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/type_traits:462:1: error: cannot template a using declaration
using _BoolConstant _LIBCPP_NODEBUG_TYPE = integral_constant<bool, _Val>;
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/type_traits:462:21: error: C++ requires a type specifier for all declarations
using _BoolConstant _LIBCPP_NODEBUG_TYPE = integral_constant<bool, _Val>;
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/type_traits:462:68: error: use of undeclared identifier '_Val'
using _BoolConstant _LIBCPP_NODEBUG_TYPE = integral_constant<bool, _Val>;
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/type_traits:462:73: error: expected '(' for function-style cast or type construction
using _BoolConstant _LIBCPP_NODEBUG_TYPE = integral_constant<bool, _Val>;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
```