[libc] enable s(n)printf without fullbuild

[michaelrj]

Summary

To use the FILE data structure, LLVM-libc must be in fullbuild mode
since it expects its own implementation. This means that (f)printf can't
be used without fullbuild, but s(n)printf only uses strings. This patch
adjusts the CMake to allow for this.

libc/config/linux/aarch64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdlib.strtoull
 
     # stdlib.h external entrypoints
     libc.src.stdlib.malloc
     libc.src.stdlib.calloc
     libc.src.stdlib.realloc
     libc.src.stdlib.free
 
+    # stdio.h entrypoints
+    libc.src.stdio.sprintf
+    libc.src.stdio.snprintf
+
     # sys/stat.h entrypoints
     libc.src.sys.stat.mkdir
     libc.src.sys.stat.mkdirat
 
     # unistd.h entrypoints
     libc.src.unistd.close
     libc.src.unistd.fsync
     libc.src.unistd.lseek
list(APPEND TARGET_LIBC_ENTRYPOINTS
     libc.src.stdio.fopen
     libc.src.stdio.fopencookie
     libc.src.stdio.fread
     libc.src.stdio.fread_unlocked
     libc.src.stdio.fseek
     libc.src.stdio.funlockfile
     libc.src.stdio.fwrite
     libc.src.stdio.fwrite_unlocked
-    libc.src.stdio.sprintf
-    libc.src.stdio.snprintf
     libc.src.stdio.fprintf
     libc.src.stdio.printf
     libc.src.stdio.stderr
     libc.src.stdio.stdout
 
     # stdlib.h entrypoints
     libc.src.stdlib._Exit
     libc.src.stdlib.atexit

libc/config/linux/x86_64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
 
     # stdlib.h external entrypoints
     libc.src.stdlib.malloc
     libc.src.stdlib.calloc
     libc.src.stdlib.realloc
     libc.src.stdlib.aligned_alloc
     libc.src.stdlib.free
 
+    # stdio.h entrypoints
+    libc.src.stdio.sprintf
+    libc.src.stdio.snprintf
+
     # sys/mman.h entrypoints
     libc.src.sys.mman.mmap
     libc.src.sys.mman.munmap
 
     # sys/stat.h entrypoints
     libc.src.sys.stat.mkdir
     libc.src.sys.stat.mkdirat
 
list(APPEND TARGET_LIBC_ENTRYPOINTS
     libc.src.stdio.fopen
     libc.src.stdio.fopencookie
     libc.src.stdio.fread
     libc.src.stdio.fread_unlocked
     libc.src.stdio.fseek
     libc.src.stdio.funlockfile
     libc.src.stdio.fwrite
     libc.src.stdio.fwrite_unlocked
-    libc.src.stdio.sprintf
-    libc.src.stdio.snprintf
     libc.src.stdio.fprintf
     libc.src.stdio.printf
     libc.src.stdio.stderr
     libc.src.stdio.stdout
 
     # signal.h entrypoints
     # TODO: Enable signal.h entrypoints after fixing signal.h
     # libc.src.signal.raise

libc/src/CMakeLists.txt

 add_subdirectory(__support)
 
 add_subdirectory(ctype)
 add_subdirectory(errno)
 add_subdirectory(fenv)
 add_subdirectory(inttypes)
 add_subdirectory(math)
 add_subdirectory(string)
 add_subdirectory(stdlib)
+add_subdirectory(stdio)
 
 if(${LIBC_TARGET_OS} STREQUAL "linux")
   add_subdirectory(dirent)
   add_subdirectory(fcntl)
   add_subdirectory(pthread)
   add_subdirectory(sys)
   add_subdirectory(unistd)
 endif()
 
 if(NOT LLVM_LIBC_FULL_BUILD)
   return()
 endif()
 
 # The signal API is currently disabled as signal.h is incorrect.
 # since assert uses the signal API, we disable assert also.
 # add_subdirectory(assert)
 # add_subdirectory(signal)
-add_subdirectory(stdio)
 add_subdirectory(threads)
 add_subdirectory(time)

libc/test/src/CMakeLists.txt

 add_subdirectory(__support)
 add_subdirectory(ctype)
 add_subdirectory(errno)
 add_subdirectory(fenv)
 add_subdirectory(inttypes)
 add_subdirectory(math)
 add_subdirectory(string)
 add_subdirectory(stdlib)
+add_subdirectory(stdio)
 
 if(${LIBC_TARGET_OS} STREQUAL "linux")
   add_subdirectory(fcntl)
   add_subdirectory(sys)
   add_subdirectory(unistd)
 endif()
 
 if(NOT LLVM_LIBC_FULL_BUILD)
   return()
 endif()
 
 add_subdirectory(dirent)
 # The signal API is currently disabled as signal.h is incorrect.
 # since assert uses the signal API, we disable assert also.
 # add_subdirectory(assert)
 # add_subdirectory(signal)
-add_subdirectory(stdio)
 add_subdirectory(time)
 
 if(${LIBC_TARGET_OS} STREQUAL "linux")
   add_subdirectory(pthread)
 endif()
 
 set(public_test ${CMAKE_CURRENT_BINARY_DIR}/public_api_test.cpp)
 

libc/utils/UnitTest/CMakeLists.txt

 target_include_directories(LibcMemoryHelpers PUBLIC ${LIBC_SOURCE_DIR})
 target_link_libraries(LibcMemoryHelpers LibcUnitTest)
 add_dependencies(
   LibcMemoryHelpers
   LibcUnitTest
   libc.src.__support.CPP.array_ref
 )
 
-if(NOT LLVM_LIBC_FULL_BUILD) # TODO(michaelrj): make a more permanant solution.
-  return()
-endif()
-
-#currently stdio is fullbuild only, so this matcher that depends on a piece of
-#printf also has to be fullbuild only.
-
 add_library(
   LibcPrintfHelpers
     PrintfMatcher.h
     PrintfMatcher.cpp
 )
 target_include_directories(LibcPrintfHelpers PUBLIC ${LIBC_SOURCE_DIR})
 target_link_libraries(LibcPrintfHelpers LibcUnitTest)
 add_dependencies(
   LibcPrintfHelpers
   LibcUnitTest
   libc.src.__support.CPP.uint128
   libc.src.stdio.printf_core.core_structs
   libc.utils.UnitTest.string_utils
 )