[llvm][cmake] never link llvm-config against llvm dylib

When cross-compiling, in order to make the output of the native and
cross-compiled llvm-config match, one needs to re-pass all cmake flags
relevant to BuildVariables.inc via `CROSS_TOOLCHAIN_FLAGS_NATIVE`. If
`LLVM_LINK_LLVM_DYLIB=ON` is among those, building a full `libLLVM` shared
object is required for the native llvm-config, otherwise `--shared-mode`
will be incorrect and `--link-shared` broken.

To avoid this, we can make llvm-config link statically against the
needed components for simplicity's sake in both the native and cross
case.

Reviewed By: beanz

Differential Revision: https://reviews.llvm.org/D116537

diff --git a/llvm/tools/llvm-config/CMakeLists.txt b/llvm/tools/llvm-config/CMakeLists.txt
index 1b74355..aa5aa20 100644 (file)
--- a/llvm/tools/llvm-config/CMakeLists.txt
+++ b/llvm/tools/llvm-config/CMakeLists.txt
@@ -6,6 +6,12 @@ set(BUILDVARIABLES_OBJPATH ${CMAKE_CURRENT_BINARY_DIR}/BuildVariables.inc)
 # Add the llvm-config tool.
 add_llvm_tool(llvm-config
   llvm-config.cpp
+  # This utility doesn't use much of LLVM, so linking a shared library for the
+  # entire thing is overkill. Avoiding that especially saves on build time when cross
+  # compiling LLVM and building both cross and native `llvm-config`s. We don't
+  # want to build an entire native libLLVM.so in addition to the cross one just
+  # for the native `llvm-config`!
+  DISABLE_LLVM_LINK_LLVM_DYLIB
   )
 
 # Compute the substitution values for various items.