cbuilder: ccgexprs sweep part 2 (#24392)

follows up #24381

This is about another 30% of ccgexprs (remaining is up to around line
3000), stopped right before the point where #24391 is required.

The `Genode::log` and `Genode::Cstring` calls in `genEcho` are left as
is but could be mangled in the future.

compiler/cbuilderstmts.nim

@@ -109,3 +109,16 @@ proc addReturn(builder: var Builder, value: string) =
   builder.add("return ")
   builder.add(value)
   builder.add(";\n")
+
+template addGoto(builder: var Builder, label: TLabel) =
+  builder.add("goto ")
+  builder.add(label)
+  builder.add(";\n")
+
+template addIncr(builder: var Builder, val: Snippet) =
+  builder.add(val)
+  builder.add("++;\n")
+
+template addDecr(builder: var Builder, val: Snippet) =
+  builder.add(val)
+  builder.add("--;\n")