[gcc(refs/users/iains/heads/d-for-darwin)] libphobos: Fix mcontext_t definitions for Darwin

[Iain D Sandoe]

https://gcc.gnu.org/g:5a667586776e48a80ab95f3cbbe2138e95432049

commit 5a667586776e48a80ab95f3cbbe2138e95432049
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date:   Mon Dec 7 15:42:09 2020 +0100

    libphobos: Fix mcontext_t definitions for Darwin

Diff:
---
 libphobos/src/std/datetime/package.d | 15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

diff --git a/libphobos/src/std/datetime/package.d b/libphobos/src/std/datetime/package.d
index 976d06ddb79..a5fd03d39e9 100644
--- a/libphobos/src/std/datetime/package.d
+++ b/libphobos/src/std/datetime/package.d
@@ -115,7 +115,6 @@ public import std.datetime.interval;
 public import std.datetime.systime;
 public import std.datetime.timezone;
 
-import core.exception : AssertError;
 import std.functional : unaryFun;
 import std.traits;
 import std.typecons : Flag, Yes, No;
@@ -267,12 +266,7 @@ public:
         StopWatch sw;
         sw.start();
         auto t1 = sw.peek();
-        bool doublestart = true;
-        try
-            sw.start();
-        catch (AssertError e)
-            doublestart = false;
-        assert(!doublestart);
+        assert(sw._flagStarted);
         sw.stop();
         assert((t1 - sw.peek()).to!("seconds", real)() <= 0);
     }
@@ -294,12 +288,7 @@ public:
         sw.start();
         sw.stop();
         auto t1 = sw.peek();
-        bool doublestop = true;
-        try
-            sw.stop();
-        catch (AssertError e)
-            doublestop = false;
-        assert(!doublestop);
+        assert(!sw._flagStarted);
         assert((t1 - sw.peek()).to!("seconds", real)() == 0);
     }