[lit] Terminate ": RUN at line N" with ";" not "&&"

This fixes projects/compiler-rt/test/fuzzer/sigusr.test, which was
broken by r333614.  The trouble was that "&&" changes the command for
which "$!" gives the pid.

llvm-svn: 333620
diff --git a/llvm/utils/lit/tests/shtest-shell.py b/llvm/utils/lit/tests/shtest-shell.py
index 016d1f6..ed0bdf35 100644
--- a/llvm/utils/lit/tests/shtest-shell.py
+++ b/llvm/utils/lit/tests/shtest-shell.py
@@ -161,7 +161,7 @@
 #
 # CHECK: FAIL: shtest-shell :: error-1.txt
 # CHECK: *** TEST 'shtest-shell :: error-1.txt' FAILED ***
-# CHECK: shell parser error on: ': \'RUN: at line 3\' && echo "missing quote'
+# CHECK: shell parser error on: ': \'RUN: at line 3\'; echo "missing quote'
 # CHECK: ***
 
 # CHECK: FAIL: shtest-shell :: error-2.txt