CI : Rectify the Clang-Related workflow issues

[bobqianic]

I found that the CI related to clang is actually not working. Firstly, we did not install clang, so it should have actually fallen back to gcc/g++. This means that we have not tested whether it compiles successfully on clang. Secondly, since we are using Docker, we should use set -e to tell the shell inside Docker to exit immediately when it encounters an error. This way, our GitHub action can catch the error, otherwise, it will be like the following situation.

https://github.com/ggerganov/whisper.cpp/actions/runs/6980309523/job/18997081462?pr=1549#step:4:1836

Before:

-- The C compiler identification is unknown
-- The CXX compiler identification is unknown
CMake Error at CMakeLists.txt:3 (project):
  The CMAKE_C_COMPILER:

    clang

  is not a full path and was not found in the PATH.

  Tell CMake where to find the compiler by setting either the environment
  variable "CC" or the CMake cache entry CMAKE_C_COMPILER to the full path to
  the compiler, or to the compiler name if it is in the PATH.


CMake Error at CMakeLists.txt:3 (project):
  The CMAKE_CXX_COMPILER:

    clang++

  is not a full path and was not found in the PATH.

  Tell CMake where to find the compiler by setting either the environment
  variable "CXX" or the CMake cache entry CMAKE_CXX_COMPILER to the full path
  to the compiler, or to the compiler name if it is in the PATH.


-- Configuring incomplete, errors occurred!

After:

-- The C compiler identification is Clang 14.0.0
-- The CXX compiler identification is Clang 14.0.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/clang - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/clang++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Could NOT find Git (missing: GIT_EXECUTABLE) 
-- Looking for pthread.h
-- Looking for pthread.h - found
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Success
-- Found Threads: TRUE  
-- CMAKE_SYSTEM_PROCESSOR: x86_64
-- x86 detected
-- SDL2_INCLUDE_DIRS = /usr/include/SDL2
-- SDL2_LIBRARIES = -L/usr/lib/x86_64-linux-gnu  -lSDL2
-- Configuring done
-- Generating done
-- Build files have been written to: /workspace