Explicitly disable git gpg signing

Otherwise building fails if the user has globally enabled gpg signing.

Fixes #1384

build_system/utils.rs

@@ -168,6 +168,8 @@ pub(crate) fn git_command<'a>(repo_dir: impl Into<Option<&'a Path>>, cmd: &str)
         .arg("user.email=dummy@example.com")
         .arg("-c")
         .arg("core.autocrlf=false")
+        .arg("-c")
+        .arg("commit.gpgSign=false")
         .arg(cmd);
     if let Some(repo_dir) = repo_dir.into() {
         git_cmd.current_dir(repo_dir);

scripts/setup_rust_fork.sh

@@ -10,7 +10,8 @@ git fetch
 git checkout -- .
 git checkout "$(rustc -V | cut -d' ' -f3 | tr -d '(')"
 
-git -c user.name=Dummy -c user.email=dummy@example.com am ../patches/*-stdlib-*.patch
+git -c user.name=Dummy -c user.email=dummy@example.com -c commit.gpgSign=false \
+    am ../patches/*-stdlib-*.patch
 
 git apply - <<EOF
 diff --git a/library/alloc/Cargo.toml b/library/alloc/Cargo.toml