fix: re-add build date to "About" page (#3464)

Co-authored-by: Felanbird <41973452+Felanbird@users.noreply.github.com>

src/common/Version.cpp

@@ -11,19 +11,15 @@ namespace chatterino {
 
 Version::Version()
 {
-    // Version
     this->version_ = CHATTERINO_VERSION;
 
-    // Commit hash
     this->commitHash_ =
         QString(FROM_EXTERNAL_DEFINE(CHATTERINO_GIT_HASH)).remove('"');
 
-    // Date of build, this is depended on the format not changing
-#ifdef CHATTERINO_NIGHTLY_VERSION_STRING
+    // Date of build file generation (≈ date of build)
+#ifdef CHATTERINO_CMAKE_GEN_DATE
     this->dateOfBuild_ =
-        QString(FROM_EXTERNAL_DEFINE(CHATTERINO_NIGHTLY_VERSION_STRING))
-            .remove('"')
-            .split(' ')[0];
+        QString(FROM_EXTERNAL_DEFINE(CHATTERINO_CMAKE_GEN_DATE)).remove('"');
 #endif
 
     // "Full" version string, as displayed in window title