main/bearssl: remove top-level exec in APKBUILD

Signed-off-by: Laurent Bercot <ska@appnovation.com>

main/bearssl/APKBUILD

-# Maintainer: Laurent Bercot <ska-devel@skarnet.org>
 # Contributor: Laurent Bercot <ska-devel@skarnet.org>
+# Maintainer: Laurent Bercot <ska-devel@skarnet.org>
 pkgname=bearssl
 pkgver=0.6_git20230221
 _pkgcommit=79c060eea3eea1257797f15ea1608a9a9923aa6f
@@ -15,7 +15,7 @@ source="
 	libbearssl.pc
 "
 
-builddir=$(pwd)/src/BearSSL-$(echo $_pkgcommit | cut -b-7)
+builddir=$PWD/src/BearSSL-${_pkgcommit:0:7}
 
 build() {
 	make \