fix missing is_component_build build arg

Without it a warning is printed.
Based on https://source.chromium.org/chromium/chromium/src/+/main:build/config/BUILDCONFIG.gn;l=173;drc=4164a6fe77902aac286464c517dc20931ea5571d

Bug: none
Change-Id: Ibc714213ef7e4c559e1830b3de9e5d3c039491f7
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/5687113
Reviewed-by: Simon Zünd <szuend@chromium.org>
Commit-Queue: Alex Rudenko <alexrudenko@chromium.org>

build_overrides/BUILDCONFIG.gn

@@ -48,6 +48,16 @@ declare_args() {
  is_debug = !is_official_build
 }
 
+declare_args() {
+ # Component build. Setting to true compiles targets declared as "components"
+ # as shared libraries loaded dynamically. This speeds up development time.
+ # When false, components will be linked statically.
+ #
+ # For more information see
+ # https://chromium.googlesource.com/chromium/src/+/main/docs/component_build.md
+ is_component_build = is_debug && current_os != "ios"
+}
+
 # ==============================================================================
 # TOOLCHAIN SETUP
 # ==============================================================================