Fix const-ness of strrchr callers.

This causes build failures in google3 where they use GCC. glibc only
provides const-correct overloads for string functions for GCC >= 4.4,
but clang -- which is what we use -- pretends to be GCC 4.2.

Change-Id: I2a054823ea6201ebcea46d5e77b80a975eefc622
diff --git a/commandline.cpp b/commandline.cpp
index f190336..d54faec 100644
--- a/commandline.cpp
+++ b/commandline.cpp
@@ -487,8 +487,8 @@
     const uint8_t* ptr = reinterpret_cast<const uint8_t*>(data);
 
     if (show_progress) {
-        char *x = strrchr(service, ':');
-        if(x) service = x + 1;
+        const char* x = strrchr(service, ':');
+        if (x) service = x + 1;
     }
 
     while (sz > 0) {
@@ -1496,7 +1496,7 @@
     int last_apk = -1;
     for (i = argc - 1; i >= 0; i--) {
         const char* file = argv[i];
-        char* dot = strrchr(file, '.');
+        const char* dot = strrchr(file, '.');
         if (dot && !strcasecmp(dot, ".apk")) {
             if (stat(file, &sb) == -1 || !S_ISREG(sb.st_mode)) {
                 fprintf(stderr, "Invalid APK file: %s\n", file);
@@ -1542,7 +1542,7 @@
     int first_apk = -1;
     for (i = argc - 1; i >= 0; i--) {
         const char* file = argv[i];
-        char* dot = strrchr(file, '.');
+        const char* dot = strrchr(file, '.');
         if (dot && !strcasecmp(dot, ".apk")) {
             if (stat(file, &sb) == -1 || !S_ISREG(sb.st_mode)) {
                 fprintf(stderr, "Invalid APK file: %s\n", file);