[krb5] Fix relative path fixup

[dg0yt]

• Fix unsuitable substitution ($(pwd) in single quotes).
• Fix wrong substitution in debug variant.

[dg0yt]

• Implements https://github.com/microsoft/vcpkg/pull/38706/files#r1606247892.
• Fixes krb5 side of [libidn2] Update to 2.3.7 [libgnutls] Fix android #37196 (comment)

/mnt/vcpkg-ci/b/kf5kio/src/v5.98.0-1c8192d833.clean/cmake/FindGSSAPI.cmake(35):  exec_program(/mnt/vcpkg-ci/installed/x64-linux/tools/krb5/bin/krb5-config ARGS --libs gssapi RETURN_VALUE _return_VALUE OUTPUT_VARIABLE GSSAPI_LIBS )
CMake Warning (dev) at cmake/FindGSSAPI.cmake:35 (exec_program):
  Policy CMP0153 is not set: The exec_program command should not be called.
  Run "cmake --help-policy CMP0153" for policy details.  Use the cmake_policy
  command to set the policy and suppress this warning.

  Use execute_process() instead.
Call Stack (most recent call first):
  /mnt/vss/_work/1/s/scripts/buildsystems/vcpkg.cmake:859 (_find_package)
  CMakeLists.txt:113 (find_package)
This warning is for project developers.  Use -Wno-dev to suppress it.

/mnt/vcpkg-ci/b/kf5kio/src/v5.98.0-1c8192d833.clean/cmake/FindGSSAPI.cmake(36):  if(_return_VALUE )
/mnt/vcpkg-ci/b/kf5kio/src/v5.98.0-1c8192d833.clean/cmake/FindGSSAPI.cmake(41):  exec_program(/mnt/vcpkg-ci/installed/x64-linux/tools/krb5/bin/krb5-config ARGS --cflags gssapi RETURN_VALUE _return_VALUE OUTPUT_VARIABLE GSSAPI_INCS )
CMake Warning (dev) at cmake/FindGSSAPI.cmake:41 (exec_program):
  Policy CMP0153 is not set: The exec_program command should not be called.
  Run "cmake --help-policy CMP0153" for policy details.  Use the cmake_policy
  command to set the policy and suppress this warning.

  Use execute_process() instead.
Call Stack (most recent call first):
  /mnt/vss/_work/1/s/scripts/buildsystems/vcpkg.cmake:859 (_find_package)
  CMakeLists.txt:113 (find_package)
This warning is for project developers.  Use -Wno-dev to suppress it.

/mnt/vcpkg-ci/b/kf5kio/src/v5.98.0-1c8192d833.clean/cmake/FindGSSAPI.cmake(42):  string(REGEX REPLACE (
?
)+$  GSSAPI_INCS -I$(pwd)/../../..//include )
/mnt/vcpkg-ci/b/kf5kio/src/v5.98.0-1c8192d833.clean/cmake/FindGSSAPI.cmake(43):  string(REGEX REPLACE  *-I ; GSSAPI_INCS -I$(pwd)/../../..//include )