main/devicepkg-dev: don't overwrite compiler-gcc.h (!141)

At least one newer kernel already includes the compiler support split
stuff, so don't overwrite it if it already exists.

main/devicepkg-dev/APKBUILD

 pkgname="devicepkg-dev"
-pkgver=0.6
+pkgver=0.7
 pkgrel=0
 pkgdesc="Provides default device package functions"
 url="https://postmarketos.org"
@@ -59,7 +59,7 @@ package() {
 sha512sums="d69930dd790b00fb39760a37d95a10899f0d167e10e2804feb05d9ce04f94185dc32d36edc90214aba2ea2aa09bf18f7dab93f1d2eff23f67beb2cc83be30e7c  compiler-gcc.h
 55943344e6c6192642f20246566c8468dba33d4ec4223c4e930f723fdb0fa248001c65a9bbaa5f15c18e9a42811c9b9decedfd5586f481aa762b6423b55d55bb  devicepkg_build.sh
 cc35989539781da2bc847fe68448863174a79db3853f836c61da064030cb729a16681cb6ffa16add558a7dba8563cb7fab495a6db811dcc3a1af5123dc0e6f72  devicepkg_package.sh
-f6074b3dfc64df3120207599b16c06768978d9bcc8c2c54afd2f566513f88c7d0cc5deabefc8dacd35929cd65e530e97a029f322c7e22193213625537f3e55ad  downstreamkernel_prepare.sh
+786673de073988aff5a4c5a4a3da07131dc693970f5492a99816e8b20caf2cd67365ed9398f74f0f0e9a0a3b5759220b9d5d79d77164357ed823ab44f364c8bc  downstreamkernel_prepare.sh
 bedf319a74bff01780192cd11c872c41a451915cc7e7542c467cd84fa1784236401f57e197258c3aae734f478c31a2052129838861ea204c0985630501f152ca  devicepkg_subpackage_kernel.sh
 9bb7f2a0930f397a713e9f4b6d5b83a426d9a2a3f692dcc42ac30717bf26ead869d8823a38f3ad388af12b2b9a02e8ec4d4418e9c2062389ed06d2b891a49ff3  deviceinfo
 136247a16ec91dc0c7241eeddb28c2196ae3b29946a9bc7e9566f848491ef1c53b12d05bf2dbc1cc352986712fd76f25c1510bcc8f301af540a2f01c33b299e1  expected-deviceinfo-downstream

main/devicepkg-dev/downstreamkernel_prepare.sh

@@ -14,7 +14,9 @@ if [ -z "$srcdir" ] || [ -z "$builddir" ] || [ -z "$_config" ] ||
 fi
 
 # support newer GCC versions
-cp -v "/usr/share/devicepkg-dev/compiler-gcc.h" "$builddir/include/linux/"
+if [ ! -f "$builddir/include/linux/compiler-gcc.h" ]; then
+        cp -v "/usr/share/devicepkg-dev/compiler-gcc.h" "$builddir/include/linux/"
+fi
 
 # Remove -Werror from all makefiles
 makefiles="$(find "$builddir" -type f -name Makefile)