Revert "Activate Spectre mitigations for SNP builds" (#4961)

.daily_canary

@@ -1,4 +1,4 @@
    ___     ___
   (- *)   (o o)   |     Y   &  +
  (  V  ) <  v  >  O    +---'---'
-/--x-m- /--m-m---xXx--/--yy-------
+/--x-m- /--m-m---xXx--/--yy-----

cmake/preproject.cmake

@@ -74,11 +74,4 @@ function(add_warning_checks name)
   )
 endfunction()
 
-set(SPECTRE_MITIGATION_FLAGS -mllvm -x86-speculative-load-hardening)
-if("${COMPILE_TARGET}" STREQUAL "snp")
-  if(NOT "${CMAKE_BUILD_TYPE}" STREQUAL "Debug")
-    add_compile_options(${SPECTRE_MITIGATION_FLAGS})
-  endif()
-endif()
-
 set(CMAKE_CXX_STANDARD 20)