Make directories in cache paths recursively

[bwarden]

When downloading cacheable files from the upstream mirror, swupd fails to write the local cached copy because it doesn't create the directories before attempting to write the files, for example:
/var/lib/swupd/cache/https___download.clearlinux.org_update/download/latest

Add a mkdir -p call to create those intermediate directories in the intended cache file path.

Failure signature:

$ sudo swupd check-update --debug -u https://download.clearlinux.org/update
Warning: Overriding version and content URLs with https://download.clearlinux.org/update
2025-04-23 10:35:19 (src/swupd_lib/curl.c:206)    Debug: Initializing swupd curl library
2025-04-23 10:35:19 (src/swupd_lib/curl.c:141)    Debug: Curl - check_connection url: https://download.clearlinux.org/update/version/latest_version
2025-04-23 10:35:19 (src/swupd_lib/curl.c:605)    Debug: Curl - Start sync download: https://download.clearlinux.org/update/version/latest_version -> <memory>
2025-04-23 10:35:19 (src/swupd_lib/curl.c:440)    Debug: Curl - process_curl_error_codes: curl_ret = 0, response = 200
2025-04-23 10:35:19 (src/swupd_lib/curl.c:623)    Debug: Curl - Complete sync download: https://download.clearlinux.org/update/version/latest_version -> <memory>, status=0
2025-04-23 10:35:19 (src/swupd_lib/progress.c:53)
2025-04-23 10:35:19 (src/swupd_lib/curl.c:605)    Debug: Curl - Start sync download: https://download.clearlinux.org/update/version/latest_version.sig -> <memory>
2025-04-23 10:35:19 (src/swupd_lib/curl.c:440)    Debug: Curl - process_curl_error_codes: curl_ret = 0, response = 200
2025-04-23 10:35:19 (src/swupd_lib/curl.c:623)    Debug: Curl - Complete sync download: https://download.clearlinux.org/update/version/latest_version.sig -> <memory>, status=0
2025-04-23 10:35:19 (src/swupd_lib/progress.c:53)
2025-04-23 10:35:19 (src/swupd_lib/curl.c:605)    Debug: Curl - Start sync download: https://download.clearlinux.org/update/43290/format -> <memory>
2025-04-23 10:35:19 (src/swupd_lib/curl.c:440)    Debug: Curl - process_curl_error_codes: curl_ret = 0, response = 200
2025-04-23 10:35:19 (src/swupd_lib/curl.c:623)    Debug: Curl - Complete sync download: https://download.clearlinux.org/update/43290/format -> <memory>, status=0
2025-04-23 10:35:19 (src/swupd_lib/progress.c:53)
2025-04-23 10:35:19 (src/swupd_lib/curl.c:385)    Error: Curl - Cannot open file '/var/lib/swupd/cache/https___download.clearlinux.org_update/download/latest' for writing - 'No such file or directory'
2025-04-23 10:35:19 (src/swupd_lib/curl.c:471)    Debug: Curl - process_curl_error_codes: curl_ret = 23, response = 0
2025-04-23 10:35:19 (src/swupd_lib/curl.c:483)    Debug: Curl - Download failed: response (0) -  ''
2025-04-23 10:35:19 (src/swupd_lib/curl.c:486)    Debug: Curl - process_curl_error_codes - curl_ret = 23
2025-04-23 10:35:19 (src/swupd_lib/curl.c:506)    Error: Curl - Error downloading to local file - ''
2025-04-23 10:35:19 (src/swupd_lib/curl.c:507)    Error: Curl - Check free space for /var/lib/swupd?
2025-04-23 10:35:19 (src/swupd_lib/curl.c:623)    Debug: Curl - Complete sync download: https://download.clearlinux.org/update/version/format41/latest -> /var/lib/swupd/cache/https___download.clearlinux.org_update/download/latest, status=6
2025-04-23 10:35:19 (src/swupd_lib/progress.c:53)

[bwarden]

Embedded tests disfavor calling dirname() outside of sys.*:

not ok 1 ANL004: Functions to avoid
# (in test file test/code_analysis/warning_functions.bats, line 44)
#   `[ "$error" -eq "0" ]' failed
# Found dirname on files:
# src/swupd_lib/curl.c:	mkdir_p(dirname(strdupa(file->path)));