ci: add an explicit, absolute CAIRO_NATIVE_RUNTIME_PATH (#782)

.cargo/config.toml

@@ -1,8 +1,13 @@
 # Required to have the proper environment variables set to
 # build the starkware-libs/sequencer dependencies with Native mode.
 
-[env]
-CAIRO_NATIVE_RUNTIME_LIBRARY = "./libcairo_native_runtime.a"
+# The `CAIRO_NATIVE_RUNTIME_LIBRARY` env variable must point to an _ABSOLUTE_ path where
+# the `libcairo_native_runtime.a` file will be stored and found.
+#
+# Since the runtime is built by the blockifier crate's build script, it will be stored
+# in blockifier's build directory, unless an absolute path is provided through this env variable.
+# This variable must be set before running `cargo build` or `cargo test`,
+# to overwrite what might be defined in a `config.toml` file.
 
 # Use `lld` for linking instead of `ld`, since we run out of memory while linking with `ld` on
 # 16-cores linux machines, see:

Makefile

@@ -84,11 +84,11 @@ ef-test-v1: build
 
 # Runs ef-tests with cairo-native mode
 ef-test-v1-native: build
-	cargo test --test tests --no-fail-fast --features "v1,native,ci" -- --nocapture
+	CAIRO_NATIVE_RUNTIME_LIBRARY=~/.cargo/libcairo_native_runtime.a cargo test --test tests --no-fail-fast --features "v1,native,ci" -- --nocapture
 
 # Build the rust crates
 build:
-	cargo build --release
+	CAIRO_NATIVE_RUNTIME_LIBRARY=~/.cargo/libcairo_native_runtime.a cargo build --release
 
 # Generates a `blockchain-tests-skip.yml` at the project root, by consuming a `data.txt` file containing logs of the ran tests
 generate-skip-file: