Compiler hangs if clang not found

[notramo]

…
38ms  compiled Wasm to C
                                                                                                            \  compiling C to native (using clang).../bin/sh: 1: clang: not found
Error: Command failed: clang porffor_tmp.c -o hello -O3 -flto=thin -march=native -s -ffast-math -fno-exceptions -fno-ident -fno-asynchronous-unwind-tables -ffunction-sections -fdata-sections

-  compiling C to native (using clang)...

The spinner continues instead of exiting with error.