test/abi-checker: run stdlib ABI stability test only when assertions are enabled

We started to diagnose new APIs such as the missing of @available attributes. This diverges
the expected change lists for builds with/without assertions enabled because some stdlib
symbols are included only when asserts are enabled. We start to require
asserts here to make sure the test doesn't fail on no-assertion settings.

Author: nkcsgexi

test/api-digester/Outputs/stability-stdlib-abi.swift.expected

@@ -9,12 +9,35 @@ Constructor __SwiftNativeNSData.init(coder:) is a new API without @available att
 Constructor __SwiftNativeNSDictionary.init(coder:) is a new API without @available attribute
 Constructor __SwiftNativeNSSet.init(coder:) is a new API without @available attribute
 
+// Should be fine, only included in stdlib when assertion is enabled.
+Func _collectReferencesInsideObject(_:) is a new API without @available attribute
+
 Func _cos(_:) has been removed
 Func _exp(_:) has been removed
 Func _exp2(_:) has been removed
+
+// Should be fine, only included in stdlib when assertion is enabled.
+Func _loadDestroyTLSCounter() is a new API without @available attribute
+
 Func _log(_:) has been removed
 Func _log10(_:) has been removed
 Func _log2(_:) has been removed
+
+// Should be fine, only included in stdlib when assertion is enabled.
+Func _measureRuntimeFunctionCountersDiffs(objects:_:) is a new API without @available attribute
+
 Func _nearbyint(_:) has been removed
 Func _rint(_:) has been removed
 Func _sin(_:) has been removed
+
+// Should be fine, only included in stdlib when assertion is enabled.
+Protocol _RuntimeFunctionCountersStats is a new API without @available attribute
+
+// Should be fine, only included in stdlib when assertion is enabled.
+Struct _GlobalRuntimeFunctionCountersState is a new API without @available attribute
+
+// Should be fine, only included in stdlib when assertion is enabled.
+Struct _ObjectRuntimeFunctionCountersState is a new API without @available attribute
+
+// Should be fine, only included in stdlib when assertion is enabled.
+Struct _RuntimeFunctionCounters is a new API without @available attribute

test/api-digester/stability-stdlib-abi.swift

@@ -1,4 +1,5 @@
 // REQUIRES: OS=macosx
+// REQUIRES: asserts
 // RUN: %empty-directory(%t.tmp)
 // mkdir %t.tmp/module-cache && mkdir %t.tmp/dummy.sdk
 // RUN: %api-digester -dump-sdk -module Swift -o %t.tmp/current-stdlib.json -module-cache-path %t.tmp/module-cache -sdk %t.tmp/dummy.sdk -abi -avoid-location