Introduce CARGO_BUILD_FLAGS

This is intended to permit passing `--release`, since dev builds are
terribly slow (e.g. 6s -> 0.2s).  See README.md for more information.

tamer/Cargo.toml

@@ -6,7 +6,13 @@ description="TAME on Rust"
 license="GPLv3+"
 edition = "2018"
 
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[profile.dev]
+# Release-level optimizations.  Spending the extra couple of moments
+# compile-time is well worth the huge savings we get at runtime.  Note that
+# this is still every so slightly slower than a release build; see other
+# profile options for release at
+# <https://doc.rust-lang.org/cargo/reference/manifest.html>.
+opt-level = 3
 
 [dependencies]
 quick-xml = ">= 0.17.0"

tamer/Makefile.am

@@ -20,8 +20,10 @@
 
 .PHONY: all
 
+CARGO_BUILD_FLAGS=@CARGO_BUILD_FLAGS@
+
 all:
-	@CARGO@ build
+	@CARGO@ build $(CARGO_BUILD_FLAGS)
 
 doc: html
 html-am:

tamer/README.md

@@ -24,3 +24,26 @@ To bootstrap from the source repository, run `./bootstrap`.
 To configure the build for your system, run `./configure`.  To build, run
 `make`.  To run tests, run `make check`.
 
+You may also invoke `cargo` directly, which `make` will do for you using
+options provided to `configure`.
+
+*Note that the default development build results in terrible runtime
+performance!*  See [#Build Flags][] below for instructions on how to
+generate a release binary.
+
+
+### Build Flags
+The environment variable `CARGO_BUILD_FLAGS` can be used to provide
+additional arguments to `cargo build` when invoked via `make`.  This can be
+provided optionally during `configure` and can be overridden when invoking
+`make`.  For example:
+
+```sh
+# release build
+$ ./configure && make CARGO_BUILD_FLAGS=--release
+$ ./configure CARGO_BUILD_FLAGS=--release && make
+
+# dev build
+$ ./configure && make
+$ ./configure CARGO_BUILD_FLAGS=--release && make CARGO_BUILD_FLAGS=
+```

tamer/configure.ac

@@ -52,6 +52,9 @@ AX_COMPARE_VERSION([$rustc_version], [ge], [$rustc_ver_req],
                    [AC_MSG_RESULT([yes ($rustc_version)])],
                    [AC_MSG_ERROR([no ($rustc_version)])])
 
+AC_ARG_VAR([CARGO_BUILD_FLAGS],
+           [Flags to be passed to `cargo build' when invoked via Make])
+
 AC_CONFIG_FILES([Makefile])
 
 AC_OUTPUT