tests/tcg/s390x: Fix test-svc with clang

clang does not support expressions involving symbols in instructions
like lghi yet, so building hello-s390x-asm.S with it fails.

Move the expression to the literal pool and load it from there.

Fixes: be4a4cb ("tests/tcg/s390x: Test single-stepping SVC")
Reported-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20230707154242.457706-1-iii@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/tcg/s390x/gdbstub/test-svc.py

@@ -25,7 +25,7 @@ def run_test():
     gdb.execute("si")
     report("larl\t" in gdb.execute("x/i $pc", False, True), "insn #2")
     gdb.execute("si")
-    report("lghi\t" in gdb.execute("x/i $pc", False, True), "insn #3")
+    report("lgrl\t" in gdb.execute("x/i $pc", False, True), "insn #3")
     gdb.execute("si")
     report("svc\t" in gdb.execute("x/i $pc", False, True), "insn #4")
     gdb.execute("si")

tests/tcg/s390x/hello-s390x-asm.S

@@ -8,7 +8,7 @@ _start:
 /* puts("Hello, World!"); */
 lghi %r2,1
 larl %r3,foo
-lghi %r4,foo_end-foo
+lgrl %r4,foo_len
 svc 4
 
 /* exit(0); */
@@ -18,3 +18,5 @@ svc 1
 .align 2
 foo: .asciz "Hello, World!\n"
 foo_end:
+.align 8
+foo_len: .quad foo_end-foo