fix: add [package].version to libgcc recipe (no source, no version)

libgcc copies libgcc_s.so from toolchain sysroot and has no [source]
section. Cookbook's guess_version had nothing to parse — no tar URL,
no git rev, no directory-name version. Added explicit version 14.2.0
(matching the cross-compiler GCC).

recipes/libs/libgcc/recipe.toml

@@ -1,3 +1,7 @@
+[package]
+name = "libgcc"
+version = "14.2.0"
+
 [build]
 template = "custom"
 script = """