[openwrt/openwrt] bpf-headers: ship a modified version of stdarg.h from musl to fix ebpf build on glibc

[LEDE Commits]

nbd pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/1b463338954e8cacd1193e097957302b389fb45e

commit 1b463338954e8cacd1193e097957302b389fb45e
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Mon Mar 7 10:37:15 2022 +0100

    bpf-headers: ship a modified version of stdarg.h from musl to fix ebpf build on glibc
    
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
 package/kernel/bpf-headers/Makefile       |  3 +++
 package/kernel/bpf-headers/files/stdarg.h | 19 +++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/package/kernel/bpf-headers/Makefile b/package/kernel/bpf-headers/Makefile
index 4d603707af..b5891a9722 100644
--- a/package/kernel/bpf-headers/Makefile
+++ b/package/kernel/bpf-headers/Makefile
@@ -106,6 +106,9 @@ define Build/InstallDev
 		$(PKG_BUILD_DIR)/scripts \
 		$(PKG_BUILD_DIR)/user_headers \
 		$(1)/bpf-headers
+	$(CP) \
+		$(CURDIR)/files/stdarg.h \
+		$(1)/bpf-headers/include
 endef
 
 $(eval $(call BuildPackage,bpf-headers))
diff --git a/package/kernel/bpf-headers/files/stdarg.h b/package/kernel/bpf-headers/files/stdarg.h
new file mode 100644
index 0000000000..603057f6e7
--- /dev/null
+++ b/package/kernel/bpf-headers/files/stdarg.h
@@ -0,0 +1,19 @@
+#ifndef _STDARG_H
+#define _STDARG_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef __builtin_va_list va_list;
+
+#define va_start(v,l)   __builtin_va_start(v,l)
+#define va_end(v)       __builtin_va_end(v)
+#define va_arg(v,l)     __builtin_va_arg(v,l)
+#define va_copy(d,s)    __builtin_va_copy(d,s)
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif