[spirv-tools] Fix build.sh script (#11888)

This bash script depends on src/tint/fuzzers/generate_spirv_corpus.py in
the dawn repo, which was deleted with:
https://dawn-review.googlesource.com/c/dawn/+/186049/5/src/tint/fuzzers/generate_spirv_corpus.py

Copy this file to the oss-fuzz repo to fix the build.

projects/spirv-tools/Dockerfile

@@ -19,3 +19,4 @@ RUN apt-get update && apt-get install -y make autoconf automake libtool ninja-bu
 RUN git clone --filter=tree:0 https://github.com/KhronosGroup/SPIRV-Tools.git spirv-tools
 WORKDIR spirv-tools
 COPY build.sh $SRC/
+COPY generate_spirv_corpus.py $SRC/

projects/spirv-tools/build.sh

@@ -15,6 +15,8 @@
 #
 ################################################################################
 
+SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd )"
+
 git clone https://github.com/KhronosGroup/SPIRV-Headers external/spirv-headers --depth=1
 git clone https://github.com/protocolbuffers/protobuf   external/protobuf      --branch v3.13.0.1
 git clone https://dawn.googlesource.com/dawn --depth=1
@@ -73,7 +75,7 @@ popd
 # Generate a corpus of SPIR-V binaries from the SPIR-V assembly files in the
 # SPIRV-Tools and tint repositories.
 mkdir $WORK/tint-binary-corpus
-python3 dawn/src/tint/fuzzers/generate_spirv_corpus.py dawn/test/tint $WORK/tint-binary-corpus standard-build/tools/spirv-as
+python3 $SCRIPT_DIR/generate_spirv_corpus.py dawn/test/tint $WORK/tint-binary-corpus standard-build/tools/spirv-as
 mkdir $WORK/spirv-binary-corpus-hashed-names
 tint_test_cases=`ls $WORK/tint-binary-corpus/*.spv`
 spirv_tools_test_cases=`find test/fuzzers/corpora -name "*.spv"`

projects/spirv-tools/generate_spirv_corpus.py

@@ -0,0 +1,90 @@
+# Copyright 2024 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+################################################################################
+
+# Collect all .spvasm files under a given directory, assemble them using
+# spirv-as, and emit the assembled binaries to a given corpus directory,
+# flattening their file names by replacing path separators with underscores.
+# If the output directory already exists, it will be deleted and re-created.
+# Files ending with ".expected.spvasm" are skipped.
+#
+# The intended use of this script is to generate a corpus of SPIR-V
+# binaries for fuzzing.
+#
+# Usage:
+#    generate_spirv_corpus.py <input_dir> <corpus_dir> <path to spirv-as>
+
+import os
+import pathlib
+import shutil
+import subprocess
+import sys
+
+
+def list_spvasm_files(root_search_dir):
+    for root, folders, files in os.walk(root_search_dir):
+        for filename in folders + files:
+            if pathlib.Path(filename).suffix == ".spvasm":
+                yield os.path.join(root, filename)
+
+
+def main():
+    if len(sys.argv) != 4:
+        print("Usage: " + sys.argv[0] +
+              " <input dir> <output dir> <spirv-as path>")
+        return 1
+    input_dir: str = os.path.abspath(sys.argv[1].rstrip(os.sep))
+    corpus_dir: str = os.path.abspath(sys.argv[2])
+    spirv_as_path: str = os.path.abspath(sys.argv[3])
+    if os.path.exists(corpus_dir):
+        shutil.rmtree(corpus_dir)
+    os.makedirs(corpus_dir)
+
+    # It might be that some of the attempts to convert SPIR-V assembly shaders
+    # into SPIR-V binaries go wrong. It is sensible to tolerate a small number
+    # of such errors, to avoid fuzzer preparation failing due to bugs in
+    # spirv-as. But it is important to know when a large number of failures
+    # occur, in case something is more deeply wrong.
+    num_errors = 0
+    max_tolerated_errors = 10
+    logged_errors = ""
+
+    for in_file in list_spvasm_files(input_dir):
+        if ".expected." in in_file:
+            continue
+        out_file = os.path.splitext(
+            corpus_dir + os.sep +
+            in_file[len(input_dir) + 1:].replace(os.sep, '_'))[0] + ".spv"
+        cmd = [
+            spirv_as_path, "--target-env", "spv1.3", in_file, "-o", out_file
+        ]
+        proc = subprocess.Popen(cmd,
+                                stdout=subprocess.PIPE,
+                                stderr=subprocess.PIPE)
+        stdout, stderr = proc.communicate()
+        if proc.returncode != 0:
+            num_errors += 1
+            logged_errors += "Error running " + " ".join(
+                cmd) + ": " + stdout.decode('utf-8') + stderr.decode('utf-8')
+
+    if num_errors > max_tolerated_errors:
+        print("Too many (" + str(num_errors) +
+              ") errors occurred while generating the SPIR-V corpus.")
+        print(logged_errors)
+        return 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())