util: use constexpr string instead of string objects

This handles an initialization order issue found with address
santization testing.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I7b3b6e980e378855e8bda8209dba18c20b67a000
diff --git a/cleanup/Makefile.am b/cleanup/Makefile.am
index 3623f7f..8f20a48 100644
--- a/cleanup/Makefile.am
+++ b/cleanup/Makefile.am
@@ -4,8 +4,7 @@
 noinst_LTLIBRARIES = libfirmwarecleanupblob_common.la
 libfirmwarecleanupblob_common_la_SOURCES = \
 	cleanup.cpp \
-	fs.cpp \
-	$(top_srcdir)/util.cpp
+	fs.cpp
 libfirmwarecleanupblob_common_la_CXXFLAGS = \
 	-flto
 libfirmwarecleanupblob_common_la_LDFLAGS = \