[Frontend] Always print current compiler version in swiftinterface flags

Swiftinterface files are always built with "current" compiler version,
which means that `-swift-compiler-version` has no effect in this context.

Author: xedin

include/swift/Option/Options.td

@@ -304,8 +304,8 @@ def package_description_version: Separate<["-"], "package-description-version">,
   MetaVarName<"<vers>">;
 
 def swift_compiler_version : Separate<["-"], "swift-compiler-version">,
-  Flags<[FrontendOption, HelpHidden, ModuleInterfaceOptionIgnorable]>,
-  HelpText<"The version of the Swift compiler used to emit swift interface and module">,
+  Flags<[FrontendOption, HelpHidden]>,
+  HelpText<"The version of the Swift compiler used to build swift interface and module">,
   MetaVarName<"<compvers>">;
 
 def tools_directory : Separate<["-"], "tools-directory">,

lib/Frontend/ModuleInterfaceSupport.cpp

@@ -124,6 +124,9 @@ static void printToolVersionAndFlagsComment(raw_ostream &out,
         !Opts.PackageFlags.IgnorableFlags.empty())
       ignorableFlags.push_back(Opts.PackageFlags.IgnorableFlags);
 
+    ignorableFlags.push_back("-swift-compiler-version");
+    ignorableFlags.push_back(version::getCompilerVersion());
+
     if (!ignorableFlags.empty()) {
       out << "// " SWIFT_MODULE_FLAGS_IGNORABLE_KEY ": ";
       llvm::interleave(

test/ModuleInterface/ModuleCache/module-cache-diagnostics.swift

@@ -61,8 +61,8 @@
 // RUN: not %target-swift-frontend -disable-implicit-concurrency-module-import -disable-implicit-string-processing-module-import -I %t -module-cache-path %t/modulecache -emit-module -o %t/TestModule.swiftmodule -module-name TestModule %s >%t/err.txt 2>&1
 // RUN: %{python} %S/Inputs/check-is-old.py %t/modulecache/OtherModule-*.swiftmodule %t/modulecache/LeafModule-*.swiftmodule
 // RUN: %FileCheck %s -check-prefix=CHECK-ERROR <%t/err.txt
-// CHECK-ERROR: LeafModule.swiftinterface:7:8: error: no such module 'NotAModule'
-// CHECK-ERROR: OtherModule.swiftinterface:4:8: error: failed to build module 'LeafModule' for importation due to the errors above; the textual interface may be broken by project issues or a compiler bug
+// CHECK-ERROR: LeafModule.swiftinterface:8:8: error: no such module 'NotAModule'
+// CHECK-ERROR: OtherModule.swiftinterface:5:8: error: failed to build module 'LeafModule' for importation due to the errors above; the textual interface may be broken by project issues or a compiler bug
 // CHECK-ERROR: module-cache-diagnostics.swift:{{[0-9]+}}:8: error: failed to build module 'OtherModule' for importation due to the errors above; the textual interface may be broken by project issues or a compiler bug
 //
 //
@@ -85,8 +85,8 @@
 // RUN: not %target-swift-frontend -disable-implicit-concurrency-module-import -disable-implicit-string-processing-module-import -I %t -module-cache-path %t/modulecache -emit-module -o %t/TestModule.swiftmodule -module-name TestModule %s >%t/err-inline.txt 2>&1
 // RUN: %{python} %S/Inputs/check-is-old.py %t/modulecache/OtherModule-*.swiftmodule %t/modulecache/LeafModule-*.swiftmodule
 // RUN: %FileCheck %s -check-prefix=CHECK-ERROR-INLINE <%t/err-inline.txt
-// CHECK-ERROR-INLINE: LeafModule.swiftinterface:6:33: error: cannot find 'unresolved' in scope
-// CHECK-ERROR-INLINE: OtherModule.swiftinterface:4:8: error: failed to build module 'LeafModule' for importation due to the errors above; the textual interface may be broken by project issues or a compiler bug
+// CHECK-ERROR-INLINE: LeafModule.swiftinterface:7:33: error: cannot find 'unresolved' in scope
+// CHECK-ERROR-INLINE: OtherModule.swiftinterface:5:8: error: failed to build module 'LeafModule' for importation due to the errors above; the textual interface may be broken by project issues or a compiler bug
 // CHECK-ERROR-INLINE: module-cache-diagnostics.swift:{{[0-9]+}}:8: error: failed to build module 'OtherModule' for importation due to the errors above; the textual interface may be broken by project issues or a compiler bug
 //
 //

test/ModuleInterface/swift-compiler-version-option.swift

@@ -4,20 +4,20 @@
 // RUN: %target-swift-frontend %s \
 // RUN:   -emit-module-path %t/Lib.swiftmodule \
 // RUN:   -emit-module-interface-path %t/Lib.swiftinterface \
-// RUN:   -enable-library-evolution -swift-version 6 \
-// RUN:   -swift-compiler-version 6.0.0.1
+// RUN:   -enable-library-evolution \
+// RUN:   -swift-version 6
 
 // RUN: %target-swift-typecheck-module-from-interface(%t/Lib.swiftinterface)
 
 /// Check option in swiftinterface
 // RUN: cat %t/Lib.swiftinterface | %FileCheck --check-prefix=CHECK-OPTION %s
-// CHECK-OPTION: swift-module-flags:
-// CHECK-SAME-OPTION: -swift-compiler-version 6.0.0.1
+// CHECK-OPTION: swift-module-flags-ignorable:
+// CHECK-SAME-OPTION: -swift-compiler-version {{.*}}
 
 /// Check option in swiftmodule
 // RUN: llvm-bcanalyzer --dump %t/Lib.swiftmodule | %FileCheck --check-prefix=CHECK-MODULE-OPTION %s
 // CHECK-MODULE-OPTION: <OPTIONS_BLOCK
-// CHECK-MODULE-OPTION: <SWIFT_COMPILER_VERSION abbrevid={{.*}}/> blob data = '6.0.0.1'
+// CHECK-MODULE-OPTION: <SWIFT_COMPILER_VERSION abbrevid={{.*}}/> blob data = '{{.*}}'
 // CHECK-MODULE-OPTION: </OPTIONS_BLOCK>
 
 public struct S {