[libc] Fix install-libc to work with LLVM_LIBC_FULL_BUILD=OFF

[lu-zero]

Initialize variables that are conditionally set to avoid undefined references in install-libc and install-libc-stripped targets:

• Initialize added_bitcode_targets to empty string (may be undefined when LIBC_TARGET_OS_IS_GPU=OFF)
• Initialize startup_target to empty string and only set to "libc-startup" when both LLVM_LIBC_FULL_BUILD=ON and NOT baremetal (startup directory is only included in full builds)
• Initialize header_install_target to empty string (may be undefined when LLVM_LIBC_FULL_BUILD=OFF)

[llvmorg-github-actions]

@llvm/pr-subscribers-libc

Author: Luca Barbato (lu-zero)

Changes

Initialize variables that are conditionally set to avoid undefined references in install-libc and install-libc-stripped targets:

• Initialize added_bitcode_targets to empty string (may be undefined when LIBC_TARGET_OS_IS_GPU=OFF)
• Initialize startup_target to empty string and only set to "libc-startup" when both LLVM_LIBC_FULL_BUILD=ON and NOT baremetal (startup directory is only included in full builds)
• Initialize header_install_target to empty string (may be undefined when LLVM_LIBC_FULL_BUILD=OFF)

---

Full diff: https://github.com/llvm/llvm-project/pull/197366.diff

1 Files Affected:

• (modified) libc/lib/CMakeLists.txt (+4-1)

diff --git a/libc/lib/CMakeLists.txt b/libc/lib/CMakeLists.txt
index 19751a9cc0736..08026e937be94 100644
--- a/libc/lib/CMakeLists.txt
+++ b/libc/lib/CMakeLists.txt
@@ -13,6 +13,7 @@ else()
 endif()
 
 set(added_archive_targets "")
+set(added_bitcode_targets "")
 foreach(archive IN ZIP_LISTS
         libc_archive_names libc_archive_targets libc_archive_entrypoint_lists)
   if(NOT ${archive_2})
@@ -69,13 +70,15 @@ foreach(file ${added_bitcode_targets})
   )
 endforeach()
 
-if(NOT LIBC_TARGET_OS_IS_BAREMETAL)
+set(startup_target "")
+if(LLVM_LIBC_FULL_BUILD AND NOT LIBC_TARGET_OS_IS_BAREMETAL)
   # For now we will disable libc-startup installation for baremetal. The
   # correct way to do it would be to make a hookable startup for baremetal
   # and install it as part of the libc installation.
   set(startup_target "libc-startup")
 endif()
 
+set(header_install_target "")
 if(LLVM_LIBC_FULL_BUILD)
   set(header_install_target install-libc-headers)
 endif()