Allow rust from repos, properly install rust-toolchain file

.SRCINFO

@@ -1,7 +1,7 @@
 pkgbase = linux-rust
 	pkgdesc = Rust Linux
 	pkgver = 6.12.9.arch1
-	pkgrel = 1
+	pkgrel = 2
 	url = https://github.com/rnestler/archpkg-linux-rust
 	arch = x86_64
 	license = GPL2
@@ -14,7 +14,8 @@ pkgbase = linux-rust
 	makedepends = pahole
 	makedepends = perl
 	makedepends = python
-	makedepends = rustup
+	makedepends = rust
+	makedepends = rust-src
 	makedepends = rust-bindgen
 	makedepends = tar
 	makedepends = xz
@@ -29,7 +30,6 @@ pkgbase = linux-rust
 	source = https://github.com/archlinux/linux/releases/download/v6.12.9-arch1/linux-v6.12.9-arch1.patch.zst
 	source = https://github.com/archlinux/linux/releases/download/v6.12.9-arch1/linux-v6.12.9-arch1.patch.zst.sig
 	source = config
-	source = rust-toolchain
 	validpgpkeys = ABAF11C65A2970B130ABE3C479BE3E4300411886
 	validpgpkeys = 647F28654894E3BD457199BE38DBBDC86092693E
 	validpgpkeys = 83BC8889351B5DEBBB68416EB8AC08600F108CDF
@@ -38,13 +38,11 @@ pkgbase = linux-rust
 	sha256sums = f57e541d26eb3971b3e587d418825c50612d75684f5ad6dd36b8084846751b5a
 	sha256sums = SKIP
 	sha256sums = 494f9b61b4893afa086d29657b1fa84948e0798217193c264055a68c7fae3380
-	sha256sums = 9cbdfdb58bcc5bbe0b6c578e62775f3d11d323ee711fa79eccdc0ac463776c1d
 	b2sums = 2584e35822a429b6825bf8d99c073848d5ba83d45b382ab82d1caa36ccbf2529036b31d4687dafb29650c87f4b63489caa2cb67a85d05183c572dcad75a35ba8
 	b2sums = SKIP
 	b2sums = 195386c83893d88d4198ddd208f4c71e1264d8f48aef50006e42581cdf6ebe441ca67a9b93bf7ed84b7580dd0b591a3ef7a06d7ee4d6ffef8486fa4962220214
 	b2sums = SKIP
 	b2sums = cb50013dc3a66c66a81bcd04b32fc627ed2166d45820ba45a9f0389416fb3e73eb425c2b1e4f135e22d9f68d089dcd8ed367d1880e0b173cf3e0e1255cb12282
-	b2sums = 731c8a43afaa9597af54611925431341f9bc1369981c0ffc455f21270ee5cd6a7de16d67d293925598ae5ca451ff425b69562b8635940fbcfa1877049b9eecb5
 
 pkgname = linux-rust
 	pkgdesc = The Linux kernel and modules with support for Rust written modules

PKGBUILD

@@ -2,7 +2,7 @@
 
 pkgbase=linux-rust
 pkgver=6.12.9.arch1
-pkgrel=1
+pkgrel=2
 pkgdesc='Rust Linux'
 url='https://github.com/rnestler/archpkg-linux-rust'
 arch=(x86_64)
@@ -17,7 +17,8 @@ makedepends=(
   pahole
   perl
   python
-  rustup
+  rust
+  rust-src
   rust-bindgen
   tar
   xz
@@ -36,7 +37,6 @@ source=(
   https://cdn.kernel.org/pub/linux/kernel/v${pkgver%%.*}.x/${_srcname}.tar.{xz,sign}
   https://github.com/archlinux/linux/releases/download/$_srctag/linux-$_srctag.patch.zst{,.sig}
   config  # the main kernel config file
-  rust-toolchain
 )
 validpgpkeys=(
   ABAF11C65A2970B130ABE3C479BE3E4300411886  # Linus Torvalds
@@ -48,14 +48,12 @@ sha256sums=('87be0360df0931b340d2bac35161a548070fbc3a8c352c49e21e96666c26aeb4'
             'SKIP'
             'f57e541d26eb3971b3e587d418825c50612d75684f5ad6dd36b8084846751b5a'
             'SKIP'
-            '494f9b61b4893afa086d29657b1fa84948e0798217193c264055a68c7fae3380'
-            '9cbdfdb58bcc5bbe0b6c578e62775f3d11d323ee711fa79eccdc0ac463776c1d')
+            '494f9b61b4893afa086d29657b1fa84948e0798217193c264055a68c7fae3380')
 b2sums=('2584e35822a429b6825bf8d99c073848d5ba83d45b382ab82d1caa36ccbf2529036b31d4687dafb29650c87f4b63489caa2cb67a85d05183c572dcad75a35ba8'
         'SKIP'
         '195386c83893d88d4198ddd208f4c71e1264d8f48aef50006e42581cdf6ebe441ca67a9b93bf7ed84b7580dd0b591a3ef7a06d7ee4d6ffef8486fa4962220214'
         'SKIP'
-        'cb50013dc3a66c66a81bcd04b32fc627ed2166d45820ba45a9f0389416fb3e73eb425c2b1e4f135e22d9f68d089dcd8ed367d1880e0b173cf3e0e1255cb12282'
-        '731c8a43afaa9597af54611925431341f9bc1369981c0ffc455f21270ee5cd6a7de16d67d293925598ae5ca451ff425b69562b8635940fbcfa1877049b9eecb5')
+        'cb50013dc3a66c66a81bcd04b32fc627ed2166d45820ba45a9f0389416fb3e73eb425c2b1e4f135e22d9f68d089dcd8ed367d1880e0b173cf3e0e1255cb12282')
 
 export KBUILD_BUILD_HOST=archlinux
 export KBUILD_BUILD_USER=$pkgbase
@@ -78,12 +76,22 @@ prepare() {
     patch -Np1 < "../$src"
   done
 
-  echo "Installing rust-src"
-  rustup component add rust-src
+  if rustup --help >/dev/null 2>&1; then
+    echo "Installing rust-src"
+    rustup component add rust-src
+  fi
 
   echo "Verifying that Rust support is available"
   make LLVM=1 rustavailable
 
+  echo "Generating rust-toolchain"
+  # We can't redirect it directly to the file, since otherwise the shell would
+  # create it empty before the rustup rustc shim starts and then rustup would
+  # complain "that empty toolchain override file detected. Please remove it, or
+  # else specify the desired toolchain properties in the file"
+  rust_version=$(rustc --version | cut -d' ' -f 2)
+  echo "$rust_version" > "$srcdir/rust-toolchain"
+
   echo "Setting config..."
   cp ../config .config
   make LLVM=1 olddefconfig
@@ -203,7 +211,7 @@ _package-headers() {
   install -Dt "$builddir/rust" -m644 scripts/target.json
   install -Dt "$builddir/rust" -m644 rust/*.rmeta
   install -Dt "$builddir/rust" -m644 rust/*.so
-  install -Dt "$builddir" -m644 ../rust-toolchain
+  install -Dt "$builddir" -m644 "$srcdir/rust-toolchain"
 
   echo "Stripping build tools..."
   local file