[libFuzzer] Update fuzzer.test to properly set environment variables.

Use env to set environment variables, so it works on Windows and Linux.

Differential Revision: https://reviews.llvm.org/D29537

llvm-svn: 294385
diff --git a/llvm/lib/Fuzzer/test/fuzzer.test b/llvm/lib/Fuzzer/test/fuzzer.test
index a3de447..9a8de79 100644
--- a/llvm/lib/Fuzzer/test/fuzzer.test
+++ b/llvm/lib/Fuzzer/test/fuzzer.test
@@ -51,7 +51,7 @@
 RUN: LLVMFuzzer-ShrinkControlFlowTest  -exit_on_src_pos=ShrinkControlFlowTest.cpp:23 2>&1 | FileCheck %s --check-prefix=EXIT_ON_SRC_POS
 EXIT_ON_SRC_POS: INFO: found line matching '{{.*}}', exiting.
 
-RUN: ASAN_OPTIONS=strict_string_checks=1 not LLVMFuzzer-StrncmpOOBTest -seed=1 -runs=1000000 2>&1 | FileCheck %s --check-prefix=STRNCMP
+RUN: env ASAN_OPTIONS=strict_string_checks=1 not LLVMFuzzer-StrncmpOOBTest -seed=1 -runs=1000000 2>&1 | FileCheck %s --check-prefix=STRNCMP
 STRNCMP: AddressSanitizer: heap-buffer-overflow
 STRNCMP-NOT: __sanitizer_weak_hook_strncmp
 STRNCMP: in LLVMFuzzerTestOneInput