Use String8/16 c_str [tools]

Bug: 295394788
Test: make checkbuild
Change-Id: I82d6899d8c15a10b15399c39177290012bb5f13b
diff --git a/tools/aapt/CrunchCache.cpp b/tools/aapt/CrunchCache.cpp
index 7b8a576..1f2febe 100644
--- a/tools/aapt/CrunchCache.cpp
+++ b/tools/aapt/CrunchCache.cpp
@@ -44,7 +44,7 @@
         // This efficiently strips the source directory prefix from our path.
         // Also, String8 doesn't have a substring method so this is what we've
         // got to work with.
-        const char* rPathPtr = mSourceFiles.keyAt(0).string()+mSourcePath.length();
+        const char* rPathPtr = mSourceFiles.keyAt(0).c_str()+mSourcePath.length();
         // Strip leading slash if present
         int offset = 0;
         if (rPathPtr[0] == OS_PATH_SEPARATOR)