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

One of the tests for the new fake use intrinsic are failing on darwin
buildbots due to relying on behaviour for their expected triple; this
commit adds explicit triples to the few remaining fake-use tests that
didn't have them.

Fixes commit 3d08ade (#86149).

Buildbot failures:
https://lab.llvm.org/buildbot/#/builders/23/builds/2505

Author: SLTozer

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

@@ -1,6 +1,6 @@
 ; assert in DAGlegalizer with fake use of half precision float.
 ; Changes to half float promotion.
-; RUN: llc -stop-after=finalize-isel -o - %s | FileCheck %s
+; RUN: llc -stop-after=finalize-isel -mtriple=x86_64-unknown-linux -o - %s | FileCheck %s
 ;
 ; CHECK:      bb.0.entry:
 ; CHECK-NEXT: %0:fr16 = FsFLD0SH

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

@@ -1,5 +1,5 @@
 ; assert in DAGlegalizer with fake use of 1-element vectors.
-; 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
 ;
 ; ModuleID = 't2.cpp'
 ; source_filename = "t2.cpp"

llvm/test/DebugInfo/X86/fake-use.ll

@@ -3,9 +3,9 @@
 ; Make sure the fake use of 'b' at the end of 'foo' causes location information for 'b'
 ; to extend all the way to the end of the function.
 
-; RUN: %llc_dwarf -O2 -filetype=obj -dwarf-linkage-names=Abstract < %s | llvm-dwarfdump --debug-info --debug-line -v - -o %t
+; RUN: %llc_dwarf -O2 -filetype=obj -mtriple=x86_64-unknown-linux -dwarf-linkage-names=Abstract < %s | llvm-dwarfdump --debug-info --debug-line -v - -o %t
 ; RUN: %python %p/../Inputs/check-fake-use.py %t
-; RUN: sed -e 's,call void (...) @llvm.fake.use,;,' %s | %llc_dwarf - -O2 -filetype=obj -dwarf-linkage-names=Abstract | llvm-dwarfdump --debug-info --debug-line -v - -o %t
+; RUN: sed -e 's,call void (...) @llvm.fake.use,;,' %s | %llc_dwarf - -O2 -filetype=obj -mtriple=x86_64-unknown-linux -dwarf-linkage-names=Abstract | llvm-dwarfdump --debug-info --debug-line -v - -o %t
 ; RUN: not %python %p/../Inputs/check-fake-use.py %t
 
 ; Generated with: