Disable Clang optimizations for Session::get*LibraryCode() functions

Clang was taking around 10 minutes to compile
`slang-embedded-core-module-source.cpp` with optimizations. Disabling
optimizations for these functions reduced the compilation time to about
12 seconds on my machine (Intel Core Ultra 7 165H), and had no
noticeable impact on run-time performance.

Run-time performance with optimizations:

```
$ hyperfine --shell=none './build/generators/Release/bin/slang-bootstrap -archive-type riff-lz4 -save-core-module-bin-source slang-core-module-generated.h -save-glsl-module-bin-source slang-glsl-module-generated.h'
Benchmark 1: ./build/generators/Release/bin/slang-bootstrap -archive-type riff-lz4 -save-core-module-bin-source slang-core-module-generated.h -save-glsl-module-bin-source slang-glsl-module-generated.h
  Time (mean ± σ):      2.545 s ±  0.035 s    [User: 2.333 s, System: 0.210 s]
  Range (min … max):    2.496 s …  2.620 s    10 runs
```

Run-time performance without optimizations:

```
$ hyperfine --shell=none './build/generators/Release/bin/slang-bootstrap -archive-type riff-lz4 -save-core-module-bin-source slang-core-module-generated.h -save-glsl-module-bin-source slang-glsl-module-generated.h'
Benchmark 1: ./build/generators/Release/bin/slang-bootstrap -archive-type riff-lz4 -save-core-module-bin-source slang-core-module-generated.h -save-glsl-module-bin-source slang-glsl-module-generated.h
  Time (mean ± σ):      2.564 s ±  0.039 s    [User: 2.350 s, System: 0.213 s]
  Range (min … max):    2.512 s …  2.614 s    10 runs
```

Disabling optimizations also makes
`slang-embedded-core-module-source.cpp.o` slightly smaller:

- 7.84 MiB with optimizations,
- 7.37 MiB without optimizations.

Fixes #9054.

Author: ncelikNV

source/slang-core-module/slang-embedded-core-module-source.cpp

@@ -326,6 +326,13 @@ struct IntrinsicOpInfo
 
 #define EMIT_LINE_DIRECTIVE() sb << "#line " << (__LINE__ + 1) << " \"" << path << "\"\n"
 
+#if SLANG_CLANG
+// Clang takes around 10 minutes to compile this file with optimizations, with EarlyCSEPass taking
+// ~95% of the execution time. Disabling optimizations here reduces the compilation time to seconds
+// and has no noticeable impact on run-time performance.
+#pragma clang optimize off
+#endif
+
 ComPtr<ISlangBlob> Session::getCoreLibraryCode()
 {
 #if SLANG_EMBED_CORE_MODULE_SOURCE
@@ -382,3 +389,7 @@ ComPtr<ISlangBlob> Session::getGLSLLibraryCode()
     return glslLibraryCode;
 }
 } // namespace Slang
+
+#if SLANG_CLANG
+#pragma clang optimize on
+#endif