[integration-tests] Specify path to the llvm bin dir instead of filecheck itself.

We can infer FileCheck's path from the llvm bin dir so there is no change today.
In the future though this will enable us to use other llvm tools to "poke" at
the produced snapshots for verification purposes.

rdar://39456714

Author: gottesmm

utils/build-script-impl

@@ -3483,15 +3483,15 @@ function build_and_test_installable_package() {
             fi
 
             LIT_EXECUTABLE_PATH="${LLVM_SOURCE_DIR}/utils/lit/lit.py"
-            FILECHECK_EXECUTABLE_PATH="$(build_directory_bin ${LOCAL_HOST} llvm)/FileCheck"
+            LLVM_BIN_DIR="$(build_directory_bin ${LOCAL_HOST} llvm)"
             echo "-- Test Installable Package --"
             call rm -rf "${PKG_TESTS_SANDBOX_PARENT}"
             call mkdir -p "${PKG_TESTS_SANDBOX}"
             with_pushd "${PKG_TESTS_SANDBOX_PARENT}" \
                 call tar xzf "${package_for_host}"
 
             with_pushd "${PKG_TESTS_SOURCE_DIR}" \
-                call python "${LIT_EXECUTABLE_PATH}" . -sv --param package-path="${PKG_TESTS_SANDBOX}" --param filecheck="${FILECHECK_EXECUTABLE_PATH}" --param test-exec-root="${PKG_TESTS_TEMPS}"
+                call python "${LIT_EXECUTABLE_PATH}" . -sv --param package-path="${PKG_TESTS_SANDBOX}" --param test-exec-root="${PKG_TESTS_TEMPS}" --param llvm-bin-dir="${LLVM_BIN_DIR}"
         fi
     fi
 }