[openwrt/openwrt] build: conditionally build llvm bpf toolchain by default

[LEDE Commits]

nbd pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/6605e45676815156f0c47d4117ee401e6616fcac

commit 6605e45676815156f0c47d4117ee401e6616fcac
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Fri Feb 7 11:11:42 2025 +0100

    build: conditionally build llvm bpf toolchain by default
    
    Unless another toolchain is present (or selected), build the bpf toolchain
    whenever a package is selected that needs it.
    
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
 include/bpf.mk                          |  2 +-
 package/network/services/unetd/Makefile |  1 +
 toolchain/Config.in                     | 14 +++++++-------
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/include/bpf.mk b/include/bpf.mk
index 2b7aa8512c..8a0121aabe 100644
--- a/include/bpf.mk
+++ b/include/bpf.mk
@@ -1,4 +1,4 @@
-BPF_DEPENDS := @HAS_BPF_TOOLCHAIN
+BPF_DEPENDS := @HAS_BPF_TOOLCHAIN + at NEED_BPF_TOOLCHAIN
 LLVM_VER:=
 
 CLANG_MIN_VER:=12
diff --git a/package/network/services/unetd/Makefile b/package/network/services/unetd/Makefile
index cc59b9100b..6923c68873 100644
--- a/package/network/services/unetd/Makefile
+++ b/package/network/services/unetd/Makefile
@@ -40,6 +40,7 @@ define Package/unetd/config
 		bool "VXLAN support"
 		depends on PACKAGE_unetd
 		depends on HAS_BPF_TOOLCHAIN
+		select NEED_BPF_TOOLCHAIN
 		default y
 
 endef
diff --git a/toolchain/Config.in b/toolchain/Config.in
index b4ba5b3b67..71ebbeb47b 100644
--- a/toolchain/Config.in
+++ b/toolchain/Config.in
@@ -40,9 +40,8 @@ menuconfig TARGET_OPTIONS
 
 	choice BPF_TOOLCHAIN
 		prompt "BPF toolchain" if DEVEL
-		default BPF_TOOLCHAIN_BUILD_LLVM if BUILDBOT
 		default BPF_TOOLCHAIN_PREBUILT if HAS_PREBUILT_LLVM_TOOLCHAIN
-		default BPF_TOOLCHAIN_NONE
+		default BPF_TOOLCHAIN_BUILD_LLVM
 
 		config BPF_TOOLCHAIN_NONE
 			bool "None"
@@ -57,7 +56,7 @@ menuconfig TARGET_OPTIONS
 			bool "Use host LLVM toolchain"
 
 		config BPF_TOOLCHAIN_BUILD_LLVM
-			select USE_LLVM_BUILD
+			select USE_LLVM_BUILD if NEED_BPF_TOOLCHAIN
 			bool "Build LLVM toolchain for eBPF"
 			help
 			  If enabled, a LLVM toolchain for building eBPF binaries will be built.
@@ -320,23 +319,24 @@ config GDB_PYTHON
 	  Enable the python bindings for GDB to allow using python in the gdb shell.
 
 config HAS_BPF_TOOLCHAIN
+	default y if !BPF_TOOLCHAIN_NONE
+	bool
+
+config NEED_BPF_TOOLCHAIN
 	bool
 
 config HAS_PREBUILT_LLVM_TOOLCHAIN
 	def_bool $(shell, [ -f llvm-bpf/.llvm-version ] && echo y || echo n)
 
 config USE_LLVM_HOST
-	select HAS_BPF_TOOLCHAIN
 	bool
 
 config USE_LLVM_PREBUILT
-	select HAS_BPF_TOOLCHAIN
 	default y if !DEVEL && !BUILDBOT && HAS_PREBUILT_LLVM_TOOLCHAIN
 	bool
 
 config USE_LLVM_BUILD
-	default y if !DEVEL && BUILDBOT
-	select HAS_BPF_TOOLCHAIN
+	default y if !DEVEL && NEED_BPF_TOOLCHAIN && (BUILDBOT || !HAS_PREBUILT_LLVM_TOOLCHAIN)
 	bool
 
 config USE_GLIBC