macOS: use homebrew gcc using version suffix. update setup instructions (#1409)

* Add version suffix to gcc on Darwin

* Update macos setup intructions

* Delete unused SConscript at tests/

* Move gcc stuff to tests/libpanda/SConscript

README.md

@@ -20,8 +20,8 @@ sudo apt-get install dfu-util gcc-arm-none-eabi python3-pip libffi-dev git
 ```
 ```bash
 # macOS
-brew tap ArmMbed/homebrew-formulae
-brew install python dfu-util arm-none-eabi-gcc gcc@12
+brew install --cask gcc-arm-embedded
+brew install python3 dfu-util gcc@12
 ```
 
 Clone panda repository:

tests/libpanda/SConscript

@@ -1,5 +1,14 @@
+import platform
+
+CC = 'gcc'
+system = platform.system()
+if system == 'Darwin':
+  # gcc installed by homebrew has version suffix (e.g. gcc-12) in order to be  
+  # distinguishable from system one - which acts as a symlink to clang
+  CC += '-12'
+
 env = Environment(
-  CC='gcc',
+  CC=CC,
   CFLAGS=[
     '-nostdlib',
     '-fno-builtin',
@@ -8,7 +17,8 @@ env = Environment(
   ],
   CPPPATH=[".", "../../board/"],
 )
-env.PrependENVPath('PATH', '/opt/homebrew/bin')
+if system == "Darwin":
+  env.PrependENVPath('PATH', '/opt/homebrew/bin')
 
 if GetOption('ubsan'):
   flags = [