Switch back to a workspace.

I switched away from a Cargo Workspace in the days before resolver="2"
was an option -- it's required to get feature resolution to be separate
per binary target in a workspace, which is in turn required because of
how the PACs abuse Cargo features.

That's been fixed for like three years, however, and a workspace
slightly reduces build times and greatly reduces target directory size.

The interaction between workspaces and .cargo/config.toml is still
frustrating -- config.toml is still the only way to set several critical
build options, but is ignored unless you CD into the relevant directory
before building, which is otherwise not required in a workspace. But,
I'll give this a shot.

Before:
- Clean build: 2m27s
- No-change rebuild: 0.428s

After:
- Clean build: 30s (!)
- rebuild: 16s :/

Cargo.toml

@@ -0,0 +1,63 @@
+[workspace]
+resolver = "2"
+members = [
+    "os",
+    "handoff",
+    "examples/*/*",
+    "testsuite",
+    "testsuite/stm32f3",
+    "testsuite/stm32f4",
+    "testsuite/stm32g0",
+    "testsuite/lm3s6965",
+]
+
+[workspace.package]
+# common defaults
+edition = "2021"
+license = "MPL-2.0"
+repository = "https://github.com/cbiffle/lilos"
+rust-version = "1.69"
+
+[workspace.dependencies]
+# Internal
+lilos = { path = "os", version = "1.0.2-pre.0", default-features = false }
+lilos-testsuite = { path = "testsuite" }
+lilos-handoff = { path = "handoff" }
+
+# External
+cfg-if = "1.0.0"
+cortex-m = {version = "0.7.4", features = ["inline-asm"]}
+cortex-m-rt = {version = "0.7.1"}
+cortex-m-semihosting = "0.5.0"
+pin-project = "1.1.5"
+panic-halt = "0.2.0"
+panic-semihosting = "0.6.0"
+futures = { version = "0.3.21", default-features = false, features = ["async-await"] }
+stm32-metapac = {version = "15.0", features = ["rt", "pac"]}
+rp2040-pac = {version = "0.3", features = ["rt"]}
+rp2040-boot2 = "0.2"
+scopeguard = { version = "1.2.0", default-features = false }
+
+#
+# Before you get excited about turning on the workspace.lints table here, note
+# that it is silently ignored by our MSRV of 1.69.
+#
+
+# Turn on some basic optimizations even in dev for space reasons.
+[profile.dev]
+codegen-units = 1       # better optimizations
+debug = true            # symbols are nice and they don't increase the size on Flash
+lto = true              # better optimizations
+opt-level = 1           # very basic optimization
+
+# The testsuite ain't tiny and doesn't fit in a 32 kiB M0 without
+# cranking up the optimization level:
+[profile.dev.package.lilos-testsuite-stm32g0]
+opt-level = "s"
+
+[profile.release]
+codegen-units = 1 # better optimizations
+debug = true # symbols are nice and they don't increase the size on Flash
+lto = true # better optimizations
+opt-level = "s"
+overflow-checks = true

README.mkdn

@@ -21,9 +21,11 @@ will find it useful too.
 
 ## Repo layout
 
-This repo contains crates in subdirectories, but it is _not_ a Cargo workspace.
-This means you will need to `cd` into subdirectories to build things. Here is a
-map:
+This repo contains crates in subdirectories, and the subdirectories use
+`.cargo/config.toml` files to change settings that Cargo has so far declined to
+allow in `Cargo.toml`, such as the target triple. This means you will need to
+`cd` into subdirectories to build things, rather than using `cargo build
+--all`. Here is a map:
 
 - `os` contains the operating system crate.
 - `testsuite` contains a test suite for the operating system, which can run on a

build-all.sh

@@ -23,6 +23,9 @@ done
 DIRS="handoff testsuite/stm32f4 testsuite/stm32g0 testsuite/stm32f3 testsuite/lm3s6965 examples/*/*/"
 
 for d in $DIRS; do
+    if [[ $d == *memory.x ]]; then
+	continue
+    fi
     echo "---- building in $d"
     pushd $d > /dev/null
     cargo build

examples/rp2040/minimal/.cargo/config.toml

@@ -2,7 +2,8 @@
 runner = "elf2uf2-rs -d"
 
 rustflags = [
-  "-C", "link-arg=-Tlink.x",
+    "-C", "link-arg=-Tlink.x",
+    "-C", "link-arg=-Lexamples/rp2040",
 ]
 
 [build]