gh-156115: Use the simulator deployment-target flag for iOS simulator builds (GH-156116)

Ensures that CFLAGS and LDFLAGS use -mios-simulator-version-min, rather
than the device-based -mios-version-min. This only matters if the CFLAGS
and LDFLAGS are used in a bare call to clang without a -target; but that is
a legal usage, so it's worth catching.
(cherry picked from commit d856402)

Co-authored-by: Clément Péron <peron.clem@gmail.com>

Author: clementperon

Misc/NEWS.d/next/Build/2026-08-20-14-02-33.gh-issue-156115.KXr8wU.rst

@@ -0,0 +1,4 @@
+iOS simulator builds are now configured with
+``-mios-simulator-version-min`` instead of the device's
+``-mios-version-min``. The device flag made the linker reject libraries
+resolved from the simulator SDK, so library detection silently failed.

configure

@@ -995,8 +995,12 @@ AS_CASE([$host],
 )
 
 dnl Add the compiler flag for the iOS minimum supported OS version.
-AS_CASE([$ac_sys_system],
-  [iOS], [
+AS_CASE([$host],
+  [*-apple-ios*-simulator], [
+    AS_VAR_APPEND([CFLAGS], [" -mios-simulator-version-min=${IPHONEOS_DEPLOYMENT_TARGET}"])
+    AS_VAR_APPEND([LDFLAGS], [" -mios-simulator-version-min=${IPHONEOS_DEPLOYMENT_TARGET}"])
+  ],
+  [*-apple-ios*], [
     AS_VAR_APPEND([CFLAGS], [" -mios-version-min=${IPHONEOS_DEPLOYMENT_TARGET}"])
     AS_VAR_APPEND([LDFLAGS], [" -mios-version-min=${IPHONEOS_DEPLOYMENT_TARGET}"])
   ],