set codegen units properly in cargo config

.cargo/config.toml.cgt

@@ -1,3 +1,4 @@
+<! local ncpus = tonumber(opt.system "nproc") !>
 [target.x86_64-unknown-linux-gnu]
 linker = "/usr/bin/clang"
 rustflags = ["-Clink-arg=-fuse-ld=lld"]
@@ -5,4 +6,7 @@ rustflags = ["-Clink-arg=-fuse-ld=lld"]
 [profile.release]
 lto = true
 opt-level = 3
-codegen-units = 1
+codegen-units = <% math.min(ncpus, 4) %>
+
+[profile.debug]
+codegen-units = <% ncpus %>

confgen.lua

@@ -57,7 +57,8 @@ cg.opt.system = function(cmd)
     if handle == nil then
         error("Failed to spawn process" .. cmd)
     end
-    return handle:read("*a"):gsub("%s+", "")
+    local data, _ = handle:read("*a"):gsub("%s$", "")
+    return data
 end
 
 -- Compile the input as lua. Meant to be used as a post-processor.