Let ecce-<app> wrappers honour an existing ECCE_HOME

The generated wrappers did "export ECCE_HOME=<builtin>" unconditionally,
overriding whatever the caller had set -- unlike the way the same
wrappers already treat ECCE_REALUSERHOME, DISPLAY and ECCE_HELP. So an
ECCE tree anywhere other than its configured location could not be run
at all, even with ECCE_HOME pointed at it.

Now "${ECCE_HOME:-<builtin>}", so the built-in path is still the default
and nothing changes for a normal install.

Found while trying to test a .deb without installing it: extracting the
package and running its wrappers silently ran the INSTALLED binaries
instead, so the test proved nothing about the package. It now works --
verified via /proc/<pid>/exe that the packaged binary is the one
running:

    dpkg-deb -x ecce_8.11.0_amd64.deb /tmp/debcheck
    ECCE_HOME=/tmp/debcheck/opt/ecce \
    ECCE_TEST_HOME=/tmp/debcheck/opt/ecce \
    ECCE_TEST_WRAPPERS=/tmp/debcheck/usr/bin \
      tests/apps/run_tests.py

which means a package can be smoke-tested before anyone installs it,
and without root.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EFMUNbw2UpRPmgsqviAowb

Author: andy

CMakeLists.txt

@@ -645,7 +645,7 @@ foreach(_gw start stop status)
   set(_gw_wrapper ${CMAKE_BINARY_DIR}/wrappers/ecce-gateway-${_gw})
   file(WRITE ${_gw_wrapper}
 "#!/bin/bash
-export ECCE_HOME=${ECCE_HOME_DIR}
+export ECCE_HOME=\${ECCE_HOME:-${ECCE_HOME_DIR}}
 export ECCE_REALUSERHOME=\${ECCE_REALUSERHOME:-$HOME}
 exec \"$ECCE_HOME/bin/ecce-gateway-${_gw}\" \"$@\"
 ")
@@ -675,7 +675,7 @@ foreach(_ds start stop status adduser)
   set(_ds_wrapper ${CMAKE_BINARY_DIR}/wrappers/ecce-dataserver-${_ds})
   file(WRITE ${_ds_wrapper}
 "#!/bin/bash
-export ECCE_HOME=${ECCE_HOME_DIR}
+export ECCE_HOME=\${ECCE_HOME:-${ECCE_HOME_DIR}}
 export ECCE_REALUSERHOME=\${ECCE_REALUSERHOME:-$HOME}
 export ECCE_REALUSER=\${ECCE_REALUSER:-\$(id -un)}
 exec \"$ECCE_HOME/bin/ecce-dataserver-${_ds}\" \"$@\"
@@ -863,7 +863,7 @@ foreach(_app ${ECCE_GUI_APPS} ${ECCE_CLI_APPS})
   endif()
   file(WRITE ${_wrapper}
 "#!/bin/bash
-export ECCE_HOME=${ECCE_HOME_DIR}
+export ECCE_HOME=\${ECCE_HOME:-${ECCE_HOME_DIR}}
 export ECCE_REALUSER=\${ECCE_REALUSER:-$(id -un)}
 export ECCE_REALUSERHOME=\${ECCE_REALUSERHOME:-$HOME}
 export HOST=\${HOST:-$(hostname)}
@@ -917,7 +917,7 @@ install(PROGRAMS ${_ecce_wrapper} DESTINATION ${ECCE_WRAPPER_DESTINATION})
 set(_viewer_wrapper ${CMAKE_BINARY_DIR}/wrappers/ecce-viewer)
 file(WRITE ${_viewer_wrapper}
 "#!/bin/bash
-export ECCE_HOME=${ECCE_HOME_DIR}
+export ECCE_HOME=\${ECCE_HOME:-${ECCE_HOME_DIR}}
 export ECCE_REALUSER=\${ECCE_REALUSER:-$(id -un)}
 export ECCE_REALUSERHOME=\${ECCE_REALUSERHOME:-$HOME}
 export HOST=\${HOST:-$(hostname)}