Update BCP computation to use derive_classpath

We now dynamically compute the classpath during startup so we need to
invoke the 'derive_classpath' program that does this during OTA to
compile everything correctly.

Test: manual OTA on blueline
Bug: 186432034
Change-Id: Iaac6718d8347c671241fbdf08ff79b0a608ad000
diff --git a/cmds/installd/file_parsing.h b/cmds/installd/file_parsing.h
index 3e2f815..88801ca 100644
--- a/cmds/installd/file_parsing.h
+++ b/cmds/installd/file_parsing.h
@@ -19,18 +19,14 @@
 
 #include <fstream>
 #include <functional>
-#include <string>
+#include <string_view>
+#include "android-base/unique_fd.h"
 
 namespace android {
 namespace installd {
 
-bool ParseFile(const std::string& strFile, std::function<bool (const std::string&)> parse) {
-    std::ifstream input_stream(strFile);
-
-    if (!input_stream.is_open()) {
-        return false;
-    }
-
+template<typename Func>
+bool ParseFile(std::istream& input_stream, Func parse) {
     while (!input_stream.eof()) {
         // Read the next line.
         std::string line;
@@ -54,6 +50,15 @@
     return true;
 }
 
+template<typename Func>
+bool ParseFile(std::string_view str_file, Func parse) {
+  std::ifstream ifs(str_file);
+  if (!ifs.is_open()) {
+    return false;
+  }
+  return ParseFile(ifs, parse);
+}
+
 }  // namespace installd
 }  // namespace android