title: CMake could not find Perl
body: <p>I am trying to build mbedcrypto using my own recipe for arm board using Yocto Linux. I am able to download and unpack the source code but during compile of the library , i get the errors</p>
  
  <pre><code>| -- Detecting C compiler ABI info
  | -- Detecting C compiler ABI info - done
  | -- Detecting C compile features
  | -- Detecting C compile features - done
  | -- Could NOT find PythonInterp (missing:  PYTHON_EXECUTABLE)
  | -- Could NOT find Perl (missing:  PERL_EXECUTABLE)
  
  </code></pre>
  
  <p>Relevant CMakeLists.txt portion as follows</p>
  
  <pre><code>
  set(CTR_DRBG_128_BIT_KEY_WARNING "${WARNING_BORDER}"
                           "${CTR_DRBG_128_BIT_KEY_WARN_L1}"
                           "${CTR_DRBG_128_BIT_KEY_WARN_L2}"
                           "${CTR_DRBG_128_BIT_KEY_WARN_L3}"
                           "${WARNING_BORDER}")
  
  
  find_package(PythonInterp)
  find_package(Perl)
  if(PERL_FOUND)
  
      # If 128-bit keys are configured for CTR_DRBG, display an appropriate warning
      execute_process(COMMAND ${PERL_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/scripts/config.pl -f ${CMAKE_CURRENT_SOURCE_DIR}/include/mbedtls/config.h get MBEDTLS_CTR_DRBG_USE_128_BIT_KEY
  
  </code></pre>
  
  <p>The error msg</p>
  
  <pre><code> Found Threads: TRUE
  | -- Could NOT find Perl (missing:  PERL_EXECUTABLE)
  | CMake Error at tests/CMakeLists.txt:15 (message):
  |   Cannot build test suites without Perl
  
  </code></pre>
  
  <p>comes from the file tests/CMakeLists.txt  which has </p>
  
  <pre><code>if(ENABLE_ZLIB_SUPPORT)
      set(libs ${libs} ${ZLIB_LIBRARIES})
  endif(ENABLE_ZLIB_SUPPORT)
  
  find_package(Perl)
  if(NOT PERL_FOUND)
      message(FATAL_ERROR "Cannot build test suites without Perl")
  endif()
  
  </code></pre>
  
  <p>I have perl installed and running at /usr/bin/perl of my host computer. I dont know if it's some cmake config or yocto issue.</p>
  
  <p>mbedcrypto recipe</p>
  
  <pre><code>DESCRIPTION = "Simple helloworld application"
  SECTION = "examples"
  DEPENDS = ""
  LICENSE = "MIT"
  LIC_FILES_CHKSUM = "file://LICENSE;md5=302d50a6369f5f22efdb674db908167a"
  SRC_URI[md5sum] = "06dd48905c236f7939d03b09bcf7f1a2"
  
  
  SRC_URI = "https://github.com/ARMmbed/mbed-crypto/archive/mbedcrypto-${PV}.tar.gz"
  
  S = "${WORKDIR}/mbed-crypto-mbedcrypto-${PV}"
  
  inherit cmake pkgconfig
  </code></pre>