Add INSTALL configuration.

tz.cpp

@@ -207,8 +207,20 @@ static std::string get_install()
     return install;
 }
 
+#ifndef INSTALL
+
 static const std::string install = get_install();
 
+#else   // INSTALL
+
+#define STRINGIZEIMP(x) #x
+#define STRINGIZE(x) STRINGIZEIMP(x)
+
+static const std::string install = STRINGIZE(INSTALL) +
+                                   std::string(1, folder_delimiter) + "tzdata";
+
+#endif  // INSTALL
+
 static
 std::string
 get_download_gz_file(const std::string& version)