Handle --ide=vs2019 switch

This restores support for VS2019 which was mistakenly removed in
https://gn-review.googlesource.com/c/gn/+/18180

Fixed: 409808513
Change-Id: I96349ea68b888913df725b70a04387b7163ae127
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/18560
Commit-Queue: David Turner <digit@google.com>
Reviewed-by: David Turner <digit@google.com>
Reviewed-by: Takuto Ikuta <tikuta@google.com>

src/gn/command_gen.cc

diff --git a/src/gn/command_gen.cc b/src/gn/command_gen.cc
index 1e53b77..d3de0ba 100644
--- a/src/gn/command_gen.cc
+++ b/src/gn/command_gen.cc
@@ -265,6 +265,8 @@
       version = VisualStudioWriter::Version::Vs2015;
     else if (ide == kSwitchIdeValueVs2017)
       version = VisualStudioWriter::Version::Vs2017;
+    else if (ide == kSwitchIdeValueVs2019)
+      version = VisualStudioWriter::Version::Vs2019;
     else if (ide == kSwitchIdeValueVs2022)
       version = VisualStudioWriter::Version::Vs2022;