lib: install qemu binfmts less often

This change ensures that 32 bit architecture targets are created by
capable hosts without qemu.

Installing qemu binfmts was unnecessary for some targets and causing
issues.

Closes #168

lib.sh.in

@@ -165,54 +165,75 @@ register_binfmt() {
 
     # In the special case where the build is native we can return
     # without doing anything else
-    if [ "${HOSTARCH%-musl}" = "${XBPS_TARGET_ARCH%-musl}" ] ; then
+    # This is only a basic check for identical archs, with more careful
+    # checks below for cases like ppc64 -> ppc and x86_64 -> i686.
+    _hostarch="${HOSTARCH%-musl}"
+    _targetarch="${XBPS_TARGET_ARCH%-musl}"
+    if [ "$_hostarch" = "$_targetarch" ] ; then
         return
     fi
 
-    case "${XBPS_TARGET_ARCH}" in
+    case "${_targetarch}" in
         armv*)
+            # TODO: detect aarch64 hosts that run 32 bit ARM without qemu (some cannot)
+            if ( [ "${_targetarch}" = "armv6l" ] && [ "${_hostarch}" = "armv7l" ] ) ; then
+                return
+            fi
+            if [ "${_targetarch}" = "armv5tel" -a \
+                \( "${_hostarch}" = "armv6l" -o "${_hostarch}" = "armv7l" \) ] ; then
+                return
+            fi
             _cpu=arm
             _magic="\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00"
             _mask="\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff"
             QEMU_BIN=qemu-arm-static
             ;;
-        aarch64*)
+        aarch64)
             _cpu=aarch64
             _magic="\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xb7"
             _mask="\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff"
             QEMU_BIN=qemu-aarch64-static
             ;;
-        ppc64le*)
+        ppc64le)
             _cpu=ppc64le
             _magic="\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x15\x00"
             _mask="\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\x00"
             QEMU_BIN=qemu-ppc64le-static
             ;;
-        ppc64*)
+        ppc64)
             _cpu=ppc64
             _magic="\x7fELF\x02\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x15"
             _mask="\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff"
             QEMU_BIN=qemu-ppc64-static
             ;;
-        ppc*)
+        ppc)
+            if [ "$_hostarch" = "ppc64" ] ; then
+                return
+            fi
             _cpu=ppc
             _magic="\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x14"
             _mask="\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff"
             QEMU_BIN=qemu-ppc-static
             ;;
-        mipsel*)
+        mipsel)
+            if [ "$_hostarch" = "mips64el" ] ; then
+                return
+            fi
             _cpu=mipsel
             _magic="\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x08\x00"
             _mask="\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff"
             QEMU_BIN=qemu-mipsel-static
             ;;
-        x86_64*)
+        x86_64)
             _cpu=x86_64
             _magic="\x7f\x45\x4c\x46\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x3e\x00"
             _mask="\xff\xff\xff\xff\xff\xfe\xfe\xfc\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff"
             QEMU_BIN=qemu-x86_64-static
             ;;
-        i686*)
+        i686)
+            if [ "$_hostarch" = "x86_64" ] ; then
+                return
+            fi
             _cpu=i386
             _magic="\x7f\x45\x4c\x46\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x03\x00"
             _mask="\xff\xff\xff\xff\xff\xfe\xfe\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff"