fix: Link conda lib during CIRCT build

Although conda lib is is LD_LIBRARY_PATH, cmake building process
still ran into erros while linking libstdc++:

```
ld:/home/centos/repo/chipyard/.conda-env/lib/libicuuc.so.73:
undefined reference to `std::condition_variable::wait(
std::unique_lock<std::mutex>&)@GLIBCXX_3.4.30'
```

Add this link flag will resolve this

scripts/build-circt-from-source.sh

@@ -75,7 +75,8 @@ echo "Building CIRCT's LLVM/MLIR"
 	  -DLLVM_TARGETS_TO_BUILD="host" \
 	  -DLLVM_ENABLE_ASSERTIONS=ON \
 	  -DCMAKE_BUILD_TYPE=RELEASE \
-	  -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
+	  -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
+	  -DCMAKE_EXE_LINKER_FLAGS="-L$RDIR/.conda-env/lib"
     ninja
 )
 
@@ -90,7 +91,8 @@ echo "Building CIRCT"
 	  -DLLVM_DIR=$RDIR/tools/circt/llvm/build/lib/cmake/llvm \
 	  -DLLVM_ENABLE_ASSERTIONS=ON \
 	  -DCMAKE_BUILD_TYPE=RELEASE \
-	  -DCMAKE_INSTALL_PREFIX=$PREFIX
+	  -DCMAKE_INSTALL_PREFIX=$PREFIX \
+	  -DCMAKE_EXE_LINKER_FLAGS="-L$RDIR/.conda-env/lib"
     ninja
 )