[Driver][SYCL] Allow for -mlong-double to be passed for SPIR target (#2729)

The use of -mlong-double was restricted to x86 and ppc.  Expand this
to allow for spir arch targets.

Author: mdtoguchi

clang/lib/Driver/ToolChains/Clang.cpp

@@ -4903,7 +4903,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   }
 
   if (Arg *A = Args.getLastArg(options::OPT_LongDouble_Group)) {
-    if (TC.getTriple().isX86())
+    if (TC.getTriple().isX86() || TC.getTriple().isSPIR())
       A->render(Args, CmdArgs);
     else if ((TC.getArch() == llvm::Triple::ppc || TC.getTriple().isPPC64()) &&
              (A->getOption().getID() != options::OPT_mlong_double_80))

clang/test/Driver/mlong-double-128.c

@@ -2,6 +2,7 @@
 // RUN: %clang -target powerpc64-pc-freebsd12 -c -### %s -mlong-double-128 2>&1 | FileCheck %s
 // RUN: %clang -target powerpc64le-linux-musl -c -### %s -mlong-double-128 2>&1 | FileCheck %s
 // RUN: %clang -target i686-linux-gnu -c -### %s -mlong-double-128 2>&1 | FileCheck %s
+// RUN: %clang -target spir64-unknown-unknown-sycldevice -c -### %s -mlong-double-128 2>&1 | FileCheck %s
 
 // RUN: %clang -target x86_64-linux-musl -c -### %s -mlong-double-128 -mlong-double-80 2>&1 | FileCheck --implicit-check-not=-mlong-double-128 /dev/null
 // RUN: %clang -target x86_64-linux-musl -c -### %s -mlong-double-80 -mlong-double-128 2>&1 | FileCheck %s

clang/test/Driver/mlong-double-64.c

@@ -3,6 +3,7 @@
 // RUN: %clang -target powerpc64le-linux-musl -c -### %s -mlong-double-64 2>&1 | FileCheck %s
 // RUN: %clang -target i686-linux-gnu -c -### %s -mlong-double-64 2>&1 | FileCheck %s
 // RUN: %clang -target x86_64-linux-musl -c -### %s -mlong-double-64 2>&1 | FileCheck %s
+// RUN: %clang -target spir64-unknown-unknown-sycldevice -c -### %s -mlong-double-64 2>&1 | FileCheck %s
 
 // CHECK: "-mlong-double-64"