cs: clone ChezScheme repo with --depth 1

INSTALL.txt

@@ -52,7 +52,7 @@ If you stick with this repository, then you have several options:
  * In-place Racket-on-Chez build --- when you use `make cs`. Unless
    you use various options described in "More Instructions: Building
    Racket-on-Chez" below, this process downloads Chez Scheme from
-   Github, builds a traditional `racket` with minimal packages, builds
+   GitHub, builds a traditional `racket` with minimal packages, builds
    Chez Scheme, and then builds Racket-on-Chez using Racket and Chez
    Scheme. Final executables that end in "cs" or "CS" are the
    Racket-on-Chez variants.

Makefile

@@ -237,6 +237,7 @@ DEFAULT_SCHEME_SRC = racket/src/build/ChezScheme
 MAKE_BUILD_SCHEME = y
 
 CHEZ_SCHEME_REPO = https://github.com/mflatt/ChezScheme
+GIT_CLONE_ARGS_qq = --depth 1
 
 # Redirected for `cs-as-is` and `cs-base`:
 BASE_TARGET = plain-minimal-in-place
@@ -315,7 +316,7 @@ scheme-src:
 
 racket/src/build/ChezScheme:
 	mkdir -p racket/src/build
-	cd racket/src/build && git clone $(CHEZ_SCHEME_REPO)
+	cd racket/src/build && git clone $(GIT_CLONE_ARGS_qq) $(CHEZ_SCHEME_REPO)
 
 update-ChezScheme:
 	cd racket/src/build/ChezScheme && git pull && git submodule update

racket/src/worksp/csbuild.rkt

@@ -54,7 +54,8 @@
 (unless (directory-exists? scheme-dir)
   (system*! "git"
 	    "clone"
-	    "git@github.com:mflatt/ChezScheme"
+            "--depth" "1"
+	    "https://github.com/mflatt/ChezScheme"
 	    scheme-dir))
 
 (unless (file-exists? (build-path scheme-dir "zlib" "Makefile"))