Hotfix/Fix broken dependency specification in CelixConfig.cmake.

[PengZheng]

This PR fixes the error when building examples standalone:

1. build and install Celix

sudo apt-get install -yq --no-install-recommends \
    build-essential \
    git \
    curl \
    uuid-dev \
    libjansson-dev \
    libcurl4-openssl-dev \
    default-jdk \
    libffi-dev \
    libzip-dev \
    libxml2-dev \
    libczmq-dev \
    libcpputest-dev \
    rapidjson-dev

cd celix
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_INSTALL_PREFIX=/home/peng/Desktop/celix ..
make -j
make install
cd ../

2. build our examples

cd examples
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_PREFIX_PATH=/home/peng/Desktop/celix ..
make

CMake Error at CMakeLists.txt:35 (find_package):
  Found package configuration file:

    /home/peng/Desktop/celix/lib/cmake/Celix/CelixConfig.cmake

  but it set Celix_FOUND to FALSE so package "Celix" is considered to be NOT
  FOUND.  Reason given by package:

  The following imported targets are referenced, but are missing:
  civetweb::civetweb

[codecov-commenter]

Codecov Report

Merging #580 (4fd5ae7) into master (a03f83d) will decrease coverage by 0.04%. The diff coverage is n/a.

:exclamation: Current head 4fd5ae7 differs from pull request most recent head 3f3daa1. Consider uploading reports for the commit 3f3daa1 to get more accurate results

@@            Coverage Diff             @@
##           master     #580      +/-   ##
==========================================
- Coverage   78.29%   78.25%   -0.05%     
==========================================
  Files         230      230              
  Lines       34999    34999              
==========================================
- Hits        27404    27390      -14     
- Misses       7595     7609      +14     

see 5 files with indirect coverage changes

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