Use String8/16 c_str [tools]

Bug: 295394788
Test: make checkbuild
Change-Id: I82d6899d8c15a10b15399c39177290012bb5f13b
diff --git a/tools/aapt/AaptUtil.cpp b/tools/aapt/AaptUtil.cpp
index 293e144..e82860d 100644
--- a/tools/aapt/AaptUtil.cpp
+++ b/tools/aapt/AaptUtil.cpp
@@ -23,7 +23,7 @@
 
 Vector<String8> split(const String8& str, const char sep) {
     Vector<String8> parts;
-    const char* p = str.string();
+    const char* p = str.c_str();
     const char* q;
 
     while (true) {
@@ -41,7 +41,7 @@
 
 Vector<String8> splitAndLowerCase(const String8& str, const char sep) {
     Vector<String8> parts;
-    const char* p = str.string();
+    const char* p = str.c_str();
     const char* q;
 
     while (true) {