[clang][ifs] Avoid assumption of default visibility in InterfaceStubs tests

[JamesNagurne]

Summary

In D63978, tests were added which expect that the default visibility is
maintained without an explicit option.

In at least one case, a downstream toolchain had the default
visibility set to 'hidden', which causes these tests to fail.

To avoid such assumptions, we can explicitly pass
-fvisibility=default to the tests that make this assumption.

[JamesNagurne]

Sadly I'm home from the weekend, so I can't post more diffs for the renaming.
Here's a link to a github search though! I think this would be all the places: https://github.com/llvm/llvm-project/search?q=iterface&unscoped_q=iterface

I nor the rest of my team have the ability to commit, so I need you to do the honors. Thanks!

clang/test/InterfaceStubs/externstatic.c

-// RUN: %clang -c -DSTORAGE="extern" -o - -emit-interface-stubs -std=c99 -xc %s | \
+// RUN: %clang -fvisibility=default -c -DSTORAGE="extern" -o - -emit-interface-stubs -std=c99 -xc %s | \
 // RUN: FileCheck -check-prefix=CHECK-EXTERN %s
 
-// RUN: %clang -DSTORAGE="extern" -O0 -o - -c -std=c99 \
+// RUN: %clang -fvisibility=default -DSTORAGE="extern" -O0 -o - -c -std=c99 \
 // RUN: -xc %s | llvm-nm - 2>&1 | FileCheck -check-prefix=CHECK-EXTERN %s
 
-// RUN: %clang -c -DSTORAGE="extern" -o - -emit-interface-stubs -std=c99 -xc %s | \
+// RUN: %clang -fvisibility=default -c -DSTORAGE="extern" -o - -emit-interface-stubs -std=c99 -xc %s | \
 // RUN: FileCheck -check-prefix=CHECK-EXTERN2 %s
 
-// RUN: %clang -DSTORAGE="extern" -O0 -o - -c -std=c99 -xc %s | llvm-nm - 2>&1 | \
+// RUN: %clang -fvisibility=default -DSTORAGE="extern" -O0 -o - -c -std=c99 -xc %s | llvm-nm - 2>&1 | \
 // RUN: FileCheck -check-prefix=CHECK-EXTERN2 %s
 
-// RUN: %clang -c -DSTORAGE="static" -o - -emit-interface-stubs -std=c99 -xc %s | \
+// RUN: %clang -fvisibility=default -c -DSTORAGE="static" -o - -emit-interface-stubs -std=c99 -xc %s | \
 // RUN: FileCheck -check-prefix=CHECK-STATIC %s
 
-// RUN: %clang -DSTORAGE="static" -O0 -o - -c -std=c99 -xc %s | llvm-nm - 2>&1 | \
+// RUN: %clang -fvisibility=default -DSTORAGE="static" -O0 -o - -c -std=c99 -xc %s | llvm-nm - 2>&1 | \
 // RUN: FileCheck -check-prefix=CHECK-STATIC %s
 
 // CHECK-EXTERN-NOT: foo
 // CHECK-STATIC-NOT: foo
 // CHECK-STATIC-NOT: bar
 
 // We want to emit extern function symbols.
 // CHECK-EXTERN2: bar
 STORAGE int foo;
 STORAGE int bar() { return 42; }

clang/test/InterfaceStubs/merge-conflict-test.c

-// RUN: not %clang -o libfoo.so -emit-interface-stubs %s %S/driver-test.c 2>&1 | FileCheck %s
+// RUN: not %clang -fvisibility=default -o libfoo.so -emit-interface-stubs %s %S/driver-test.c 2>&1 | FileCheck %s
 // CHECK: error: Interface Stub: Type Mismatch
-int foo;
+int foo;
 

clang/test/InterfaceStubs/object-float.c

-// RUN: not %clang -o - -emit-interface-stubs %s %S/object.c 2>&1 | FileCheck %s
+// RUN: not %clang -fvisibility=default -o - -emit-interface-stubs %s %S/object.c 2>&1 | FileCheck %s
 // CHECK: error: Interface Stub: Size Mismatch
-double data = 42.0;
+double data = 42.0;
 

clang/test/InterfaceStubs/object.c

-// RUN: %clang -c -o - -emit-interface-stubs %s | FileCheck -check-prefix=CHECK-TAPI %s
-// RUN: %clang -c -o - -emit-interface-stubs %s | FileCheck -check-prefix=CHECK-SYMBOLS %s
-// RUN: %clang -c -o - %s | llvm-nm - 2>&1 | FileCheck -check-prefix=CHECK-SYMBOLS %s
+// RUN: %clang -fvisibility=default -c -o - -emit-interface-stubs %s | FileCheck -check-prefix=CHECK-TAPI %s
+// RUN: %clang -fvisibility=default -c -o - -emit-interface-stubs %s | FileCheck -check-prefix=CHECK-SYMBOLS %s
+// RUN: %clang -fvisibility=default -c -o - %s | llvm-nm - 2>&1 | FileCheck -check-prefix=CHECK-SYMBOLS %s
 
 // CHECK-TAPI: data: { Type: Object, Size: 4 }
 // CHECK-SYMBOLS: data
 int data = 42;