test: explicitly indicate interpreter for utils

This fixes the last couple of instances of the interpreter not being
passed to the python the scripts which makes them fail on OSes where
shebangs are not honoured (i.e. Windows)

Author: compnerd

test/Runtime/backtrace.swift

@@ -1,6 +1,6 @@
 // RUN: %empty-directory(%t)
 // RUN: %target-build-swift %s -o %t/a.out
-// RUN: not --crash %t/a.out 2>&1 | %utils/backtrace-check
+// RUN: not --crash %t/a.out 2>&1 | %{python} %utils/backtrace-check
 
 // This is not supported on watchos, ios, or tvos
 // UNSUPPORTED: OS=watchos

test/Runtime/linux-fatal-backtrace.swift

@@ -1,6 +1,6 @@
 // RUN: %empty-directory(%t)
 // RUN: %target-build-swift %s -o %t/a.out
-// RUN: not --crash %t/a.out 2>&1 | PYTHONPATH=%lldb-python-path %utils/symbolicate-linux-fatal %t/a.out - | %utils/backtrace-check -u
+// RUN: not --crash %t/a.out 2>&1 | PYTHONPATH=%lldb-python-path %{python} %utils/symbolicate-linux-fatal %t/a.out - | %{python} %utils/backtrace-check -u
 // REQUIRES: executable_test
 // REQUIRES: OS=linux-gnu
 // REQUIRES: lldb

test/expr/primary/selector/fixits.swift

@@ -20,7 +20,7 @@
 // RUN: %empty-directory(%t.remapping)
 // RUN: cp %s %t.sources/fixits.swift
 // RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk-nosource -I %t.overlays) -typecheck %t.sources/fixits.swift -fixit-all -emit-fixits-path %t.remapping/fixits.remap
-// RUN: %utils/apply-fixit-edits.py %t.remapping
+// RUN: %{python} %utils/apply-fixit-edits.py %t.remapping
 // RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk-nosource -I %t.overlays) -typecheck %t.sources/fixits.swift 2> %t.result
 
 // RUN: %FileCheck %s < %t.result