Make deps: Compile own nasm for Linux

This solves annoyance that the official RPM repository of nasm requires
newer version of rpm tool compared to what is shipped by default with
centOS 7.

Differential Revision: https://developer.blender.org/D8905

build_files/build_environment/CMakeLists.txt

@@ -34,7 +34,7 @@
 #   Run "make deps" from main Blender directory
 #
 # LINUX USAGE:
-#   Install compiler cmake autoconf automake libtool yasm nasm tcl
+#   Install compiler cmake autoconf automake libtool yasm tcl
 #   Run "make deps" from main Blender directory
 #
 ####################################################################################################
@@ -75,6 +75,8 @@ include(cmake/llvm.cmake)
 include(cmake/clang.cmake)
 if(APPLE)
   include(cmake/openmp.cmake)
+endif()
+if(UNIX)
   include(cmake/nasm.cmake)
 endif()
 include(cmake/openimageio.cmake)

build_files/build_environment/cmake/check_software.cmake

@@ -54,7 +54,7 @@ if(UNIX)
       "  ${_software_missing}\n"
       "\n"
       "On Debian and Ubuntu:\n"
-      "  apt install autoconf automake libtool yasm nasm tcl\n"
+      "  apt install autoconf automake libtool yasm tcl\n"
       "\n"
       "On macOS (with homebrew):\n"
       "  brew install autoconf automake bison libtool pkg-config yasm\n"

build_files/build_environment/cmake/ffmpeg.cmake

@@ -52,6 +52,11 @@ if(APPLE)
     --target-os=darwin
     --x86asmexe=${LIBDIR}/nasm/bin/nasm
   )
+elseif(UNIX)
+  set(FFMPEG_EXTRA_FLAGS
+    ${FFMPEG_EXTRA_FLAGS}
+    --x86asmexe=${LIBDIR}/nasm/bin/nasm
+  )
 endif()
 
 ExternalProject_Add(external_ffmpeg
@@ -142,7 +147,7 @@ if(WIN32)
     external_zlib_mingw
   )
 endif()
-if(APPLE)
+if(UNIX)
   add_dependencies(
     external_ffmpeg
     external_nasm

build_files/build_environment/cmake/x264.cmake

@@ -34,6 +34,12 @@ else()
   set(X264_CONFIGURE_ENV echo .)
 endif()
 
+if(UNIX AND NOT APPLE)
+  set(X264_CONFIGURE_ENV
+    export AS=${LIBDIR}/nasm/bin/nasm
+  )
+endif()
+
 ExternalProject_Add(external_x264
   URL ${X264_URI}
   DOWNLOAD_DIR ${DOWNLOAD_DIR}
@@ -54,7 +60,7 @@ if(MSVC)
   set_target_properties(external_x264 PROPERTIES FOLDER Mingw)
 endif()
 
-if(APPLE)
+if(UNIX)
   add_dependencies(
     external_x264
     external_nasm