Remove build.rs.

This was more useful at the time when we were determining, e.g., optimal lookup
table sizes and could regenerate them more easily, but it came at a massive
complexity cost.  It also meant that we were unable to implement backend
autoselection.  This commit removes the `build.rs` entirely.  In the future, a
different `build.rs` could be added that auto-selects a backend, but it seems
like the current default-u64 setup has been working fine.

Cargo.toml

@@ -16,7 +16,6 @@ exclude = [
     ".gitignore",
     ".travis.yml",
 ]
-build = "build.rs"
 
 [package.metadata.docs.rs]
 # Disabled for now since this is borked; tracking https://github.com/rust-lang/docs.rs/issues/302
@@ -37,12 +36,6 @@ rand = "0.6"
 name = "dalek_benchmarks"
 harness = false
 
-# Note: we generate precomputed tables by building the crate twice: once as
-# part of build.rs, and then once "for real".
-#
-# This means that the [dependencies] and [build-dependencies] sections must
-# match exactly, since the build.rs uses the crate itself as a library.
-
 [dependencies]
 rand_core = { version = "0.3.0", default-features = false }
 byteorder = { version = "^1.2.3", default-features = false, features = ["i128"] }
@@ -52,34 +45,18 @@ subtle = { version = "2", default-features = false }
 serde = { version = "1.0", default-features = false, optional = true }
 packed_simd = { version = "0.3.0", features = ["into_bits"], optional = true }
 
-[build-dependencies]
-rand_core = { version = "0.3.0", default-features = false }
-byteorder = { version = "^1.2.3", default-features = false, features = ["i128"] }
-digest = { version = "0.8", default-features = false }
-clear_on_drop = "=0.2.3"
-subtle = { version = "2", default-features = false }
-serde = { version = "1.0", default-features = false, optional = true }
-packed_simd = { version = "0.3.0", features = ["into_bits"], optional = true }
-
 [features]
 nightly = ["subtle/nightly", "clear_on_drop/nightly"]
 default = ["std", "u64_backend"]
 std = ["alloc", "subtle/std", "rand_core/std"]
 alloc = []
-yolocrypto = []
 
 # The u32 backend uses u32s with u64 products.
 u32_backend = []
 # The u64 backend uses u64s with u128 products.
 u64_backend = []
 # The SIMD backend uses parallel formulas, using either AVX2 or AVX512-IFMA.
 simd_backend = ["nightly", "u64_backend", "packed_simd"]
-# Old name for the SIMD backend, preserved for compatibility
+# DEPRECATED: this is now an alias for `simd_backend` and may be removed
+# in some future release.
 avx2_backend = ["simd_backend"]
-
-# Signals that we're in the main build stage.  This is off by default,
-# to signal stage 1 of the build, where build.rs loads the library
-# into the build script. Then, the build.rs emits the stage2_build
-# feature before the main-stage compilation.
-stage2_build = []
-

src/backend/serial/scalar_mul/mod.rs

@@ -18,7 +18,6 @@
 
 pub mod variable_base;
 
-#[cfg(feature = "stage2_build")]
 pub mod vartime_double_base;
 
 #[cfg(feature = "alloc")]