SCons: Move platform logo/run icon to export folder

Follow-up to #75932.
Since these icons are only used by the export plugin, it makes sense to
move them and generate the headers there.

The whole `detect.is_active()` logic seems to be a leftover from before
times, as far back as 1.0-stable it already wasn't used for anything.

So I'm removing it and moving the export icon generation to
`platform_methods`, where it makes more sense.

platform_methods.py

@@ -110,3 +110,33 @@ def detect_arch():
         print("Unsupported CPU architecture: " + host_machine)
         print("Falling back to x86_64.")
         return "x86_64"
+
+
+def generate_export_icons(platform_path, platform_name):
+    """
+    Generate headers for logo and run icon for the export plugin.
+    """
+    export_path = platform_path + "/export"
+    svg_names = []
+    if os.path.isfile(export_path + "/logo.svg"):
+        svg_names.append("logo")
+    if os.path.isfile(export_path + "/run_icon.svg"):
+        svg_names.append("run_icon")
+
+    for name in svg_names:
+        svgf = open(export_path + "/" + name + ".svg", "rb")
+        b = svgf.read(1)
+        svg_str = " /* AUTOGENERATED FILE, DO NOT EDIT */ \n"
+        svg_str += " static const char *_" + platform_name + "_" + name + '_svg = "'
+        while len(b) == 1:
+            svg_str += "\\" + hex(ord(b))[1:]
+            b = svgf.read(1)
+
+        svg_str += '";\n'
+
+        svgf.close()
+
+        # NOTE: It is safe to generate this file here, since this is still executed serially.
+        wf = export_path + "/" + name + "_svg.gen.h"
+        with open(wf, "w") as svgw:
+            svgw.write(svg_str)