[Apple Silicon] Adjust linking deployment target from 11.0 down to 10.16 on x86.

Author: shahmishal

lib/Driver/DarwinToolChains.cpp

@@ -618,6 +618,14 @@ toolchains::Darwin::addDeploymentTargetArgs(ArgStringList &Arguments,
           micro = 0;
         }
 
+        // Temporary hack: adjust macOS version passed to the linker from
+        // 11 down to 10.16, but only for x86.
+        if (triple.isX86() && major == 11) {
+          major = 10;
+          minor = 16;
+          micro = 0;
+        }
+
         break;
       case DarwinPlatformKind::IPhoneOS:
       case DarwinPlatformKind::IPhoneOSSimulator:

test/Driver/linker.swift

@@ -109,10 +109,18 @@
 // Check arm64 macOS first deployment version adjustment.
 // RUN: %swiftc_driver -driver-print-jobs -target arm64-apple-macosx10.15.1 %s 2>&1 | %FileCheck -check-prefix ARM64E_MACOS_LINKER %s
 
+// Check x86 macOS 11 deployment version adjustment.
+// RUN: %swiftc_driver -driver-print-jobs -target x86_64-apple-macosx11.0 %s 2>&1 | %FileCheck -check-prefix X86_MACOS11_LINKER %s
+// RUN: %swiftc_driver -driver-print-jobs -target arm64-apple-macosx11.0 %s 2>&1 | %FileCheck -check-prefix ARM64E_MACOS_LINKER %s
+
 // MACOS_10_15: -platform_version macos 10.9.0 10.15.0
 // MACOS_10_15_4: -platform_version macos 10.9.0 10.15.4
 // MACOS_UNVERSIONED: -platform_version macos 10.9.0 0.0.0
 
+// ARM64E_MACOS_LINKER: -platform_version macos 11.0.0
+// X86_MACOS11_LINKER: -platform_version macos 10.16.0
+// X86_64_WATCHOS_SIM_LINKER: -platform_version watchos-simulator 7.0.0
+
 // There are more RUN lines further down in the file.
 
 // CHECK: swift