dmd-bootstrap: remove build_wrksrc for patching

srcpkgs/dmd-bootstrap/template

@@ -6,7 +6,6 @@ _gitrev_dmd=75266348c8a2368945a339ab86d7c8960a9bfc08
 _gitrev_druntime=33ae38cef41564b12864470afaf8430eb7334d3b
 _gitrev_phobos=30ac23a0889dd183221ce531a057171dd45296c4
 create_wrksrc=yes
-build_wrksrc="dmd/src"
 build_style=gnu-makefile
 provides="d-compiler-${version}_${revision}"
 only_for_archs="x86_64 x86_64-musl i686 i686-musl"
@@ -44,6 +43,7 @@ do_build() {
 		i686*)    bits=32;;
 	esac
 
+	cd dmd/src
 	make ${makejobs} -f posix.mak HOST_CXX=$CXX MODEL=$bits TARGET_CPU=X86 RELEASE=1 all
 	dmd=${wrksrc}/dmd/src/dmd
 
@@ -62,6 +62,7 @@ do_install() {
 		i686*)    bits=32;;
 	esac
 
+	cd dmd/src
 	vbin dmd
 
 	vmkdir etc