[test] Fix load-invalid-arch.swift to use the "major" architecture (#17342)

armv7, armv7s, and armv7k all get encoded as "arm" in today's scheme
for swiftmodules, so we can't just use the CPU part of the triple as
the expected swiftmodule architecture in the diagnostic.

Author: jrose-apple

test/Serialization/load-invalid-arch.swift

@@ -5,13 +5,13 @@
 // RUN: touch %t/new_module.swiftmodule/ppc65.swiftmodule
 // RUN: touch %t/new_module.swiftmodule/i387.swiftdoc
 // RUN: touch %t/new_module.swiftmodule/ppc65.swiftdoc
-// RUN: not %target-swift-frontend %s -typecheck -I %t -show-diagnostics-after-fatal 2>&1 | %FileCheck %s -DTARGET_ARCHITECTURE=%target-cpu
+// RUN: not %target-swift-frontend %s -typecheck -I %t -show-diagnostics-after-fatal 2>&1 | %FileCheck %s -DTARGET_ARCHITECTURE=$(echo %target-swiftmodule-name | cut -d. -f1)
 
 // RUN: %empty-directory(%t)
 // RUN: mkdir -p %t/new_module.framework/Modules/new_module.swiftmodule/
 // RUN: touch %t/new_module.framework/Modules/new_module.swiftmodule/i387.swiftmodule
 // RUN: touch %t/new_module.framework/Modules/new_module.swiftmodule/ppc65.swiftmodule
-// RUN: not %target-swift-frontend %s -F %t -typecheck -show-diagnostics-after-fatal 2>&1 | %FileCheck %s -DTARGET_ARCHITECTURE=%target-cpu
+// RUN: not %target-swift-frontend %s -F %t -typecheck -show-diagnostics-after-fatal 2>&1 | %FileCheck %s -DTARGET_ARCHITECTURE=$(echo %target-swiftmodule-name | cut -d. -f1)
 
 //CHECK: {{.*}} error: could not find module 'new_module' for architecture '[[TARGET_ARCHITECTURE]]'; found: {{ppc65, i387|i387, ppc65}}
 //CHECK-NEXT: import new_module