Allow setting LLVM_EXPERIMENTAL_TARGETS_TO_BUILD to "all"

[arichardson]

Summary

When set to "all" we will now build all experimental targets. This matches
the behaviour for LLVM_TARGETS_TO_BUILD.

[arichardson]

ping

[beanz]

LGTM

[foad]

@arichardson thank you for doing this!

[barannikov88]

Thanks, always wanted to do this, but never had time.

llvm/CMakeLists.txt

set(LLVM_ALL_TARGETS
   Sparc
   SystemZ
   VE
   WebAssembly
   X86
   XCore
   )
 
+set(LLVM_ALL_EXPERIMENTAL_TARGETS
+  ARC
+  CSKY
+  DirectX
+  M68k
+  SPIRV
+  Xtensa
+)
+
 # List of targets with JIT support:
 set(LLVM_TARGETS_WITH_JIT X86 PowerPC AArch64 ARM Mips SystemZ)
 
 set(LLVM_TARGETS_TO_BUILD "all"
     CACHE STRING "Semicolon-separated list of targets to build, or \"all\".")
 
 set(LLVM_EXPERIMENTAL_TARGETS_TO_BUILD ""
-    CACHE STRING "Semicolon-separated list of experimental targets to build.")
+    CACHE STRING "Semicolon-separated list of experimental targets to build, or \"all\".")
 
 option(BUILD_SHARED_LIBS
   "Build all libraries as shared libraries instead of static" OFF)
 
 option(LLVM_ENABLE_BACKTRACES "Enable embedding backtraces on crash." ON)
 if(LLVM_ENABLE_BACKTRACES)
   set(ENABLE_BACKTRACES 1)
 endif()

 
 set(LLVM_ENABLE_Z3_SOLVER_DEFAULT "${Z3_FOUND}")
 
 
 if( LLVM_TARGETS_TO_BUILD STREQUAL "all" )
   set( LLVM_TARGETS_TO_BUILD ${LLVM_ALL_TARGETS} )
 endif()
 
+if(LLVM_EXPERIMENTAL_TARGETS_TO_BUILD STREQUAL "all")
+  set(LLVM_EXPERIMENTAL_TARGETS_TO_BUILD ${LLVM_ALL_EXPERIMENTAL_TARGETS})
+endif()
+
 set(LLVM_TARGETS_TO_BUILD
    ${LLVM_TARGETS_TO_BUILD}
    ${LLVM_EXPERIMENTAL_TARGETS_TO_BUILD})
 list(REMOVE_DUPLICATES LLVM_TARGETS_TO_BUILD)
 
 option(LLVM_ENABLE_PIC "Build Position-Independent Code" ON)
 option(LLVM_ENABLE_MODULES "Compile with C++ modules enabled." OFF)
 if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")