[ExtendLifetimes][NFC] Add explicit triple to new fake-use tests

Several tests for the new fake use intrinsic are failing on NVPTX
buildbots due to relying on behaviour for their expected triple;
this commit adds that triple to each of them to prevent failures.

Fixes commit 3d08ade (#86149).

Example buildbot failures:
https://lab.llvm.org/buildbot/#/builders/160/builds/4175
https://lab.llvm.org/buildbot/#/builders/180/builds/4173

Author: SLTozer

llvm/test/CodeGen/MIR/X86/fake-use-tailcall.mir

@@ -22,7 +22,7 @@
 #   return temp;
 # }
 #
-# RUN: llc -run-pass=codegenprepare -o - %s | FileCheck %s
+# RUN: llc -run-pass=codegenprepare -mtriple=x86_64-unknown-linux -o - %s | FileCheck %s
 #
 # CHECK:      define{{.*}}foo
 # CHECK:      if.then:

llvm/test/CodeGen/X86/fake-use-scheduler.mir

@@ -1,5 +1,5 @@
 # Prevent the machine scheduler from moving instructions past FAKE_USE.
-# RUN: llc -run-pass machine-scheduler -debug-only=machine-scheduler 2>&1 -o - %s | FileCheck %s
+# RUN: llc -run-pass machine-scheduler -mtriple=x86_64-unknown-linux -debug-only=machine-scheduler 2>&1 -o - %s | FileCheck %s
 # REQUIRES: asserts
 #
 # We make sure that, beginning with the first FAKE_USE instruction,

llvm/test/CodeGen/X86/fake-use-tailcall.ll

@@ -1,4 +1,4 @@
-; RUN: llc < %s -stop-after=finalize-isel - | FileCheck %s --implicit-check-not FAKE_USE
+; RUN: llc < %s -stop-after=finalize-isel -mtriple=x86_64-unknown-linux - | FileCheck %s --implicit-check-not FAKE_USE
 ; Fake uses following tail calls should be pulled in front
 ; of the TCRETURN instruction. Fake uses using something defined by
 ; the tail call or after it should be suppressed.

llvm/test/CodeGen/X86/fake-use-vector2.ll

@@ -1,4 +1,4 @@
-; RUN: llc -stop-after=finalize-isel -filetype=asm -o - %s | FileCheck %s
+; RUN: llc -stop-after=finalize-isel -mtriple=x86_64-unknown-linux -filetype=asm -o - %s | FileCheck %s
 ;
 ; Make sure we can split vectors that are used as operands of FAKE_USE.
 

llvm/test/CodeGen/X86/fake-use-zero-length.ll

@@ -1,4 +1,4 @@
-; RUN: llc < %s -stop-after=finalize-isel | FileCheck %s --implicit-check-not=FAKE_USE
+; RUN: llc < %s -stop-after=finalize-isel -mtriple=x86_64-unknown-linux | FileCheck %s --implicit-check-not=FAKE_USE
 ;
 ; Make sure SelectionDAG does not crash handling fake uses of zero-length arrays
 ; and structs. Check also that they are not propagated.